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Sample records for growth regime characterization

  1. Growth regimes during homoepitaxial growth of GaN by ammonia molecular beam epitaxy

    SciTech Connect

    Corrion, A. L.; Wu, F.; Speck, J. S.

    2012-09-01

    c-plane GaN films were grown by ammonia molecular beam epitaxy on metal-organic chemical vapor deposition templates for a wide range of NH{sub 3}:Ga flux ratios and growth temperatures, and the resulting films were characterized using atomic force microscopy, reflection high-energy electron diffraction, and transmission electron microscopy. Three distinct nitrogen-rich growth regimes - unstable layer-by-layer, quasi-stable step flow, and dislocation-mediated pitting - were identified based on the growth mode and film properties. In addition, step flow growth was observed under conditions of gallium droplet accumulation. The results indicate the existence of two regimes for step-flow growth of GaN by ammonia MBE - both gallium-rich and nitrogen-rich. Growth mode instabilities and mound formation were observed and are discussed in the context of a step-edge energy barrier to adatom diffusion over a terrace.

  2. Ballooning filament growth in the intermediate nonlinear regime

    SciTech Connect

    Zhu, P.; Hegna, C. C.

    2008-09-15

    A theory is developed for the description of ballooning instability in the intermediate nonlinear regime for general magnetic configurations including toroidal systems such as tokamaks. The evolution equations for the plasma filament growth induced by the ballooning instability are derived accounting for the dominant nonlinear effects in an ideal magnetohydrodynamic description. The intermediate nonlinear regime of ballooning modes is defined by the ordering that the plasma filament displacement across the magnetic surface is comparable to the linear mode width in the same direction. In the tokamak case, this regime could become particularly relevant for a transport barrier as the width of the barrier (or pedestal) region approaches the mode width of the dominant ballooning mode. A remarkable feature of the nonlinear ballooning equations is that solutions of the associated local linear ballooning mode equations continue to be valid solutions into the intermediate nonlinear regime. The filament growth equations for the intermediate nonlinear ballooning regime may be applicable to the precursor and precollapse phase of edge localized modes observed in both simulations and experiments.

  3. Coarsening foams robustly reach a self-similar growth regime.

    PubMed

    Lambert, Jérôme; Mokso, Rajmund; Cantat, Isabelle; Cloetens, Peter; Glazier, James A; Graner, François; Delannay, Renaud

    2010-06-18

    Dry liquid foams coarsen like other diphasic systems governed by interfacial energy: gas slowly diffuses across liquid films, resulting in large bubbles growing at the expense of smaller ones which eventually shrink and disappear. A foam scatters light very effectively, preventing direct optical observation of bubble sizes and shapes in large foams. Using high speed x-ray tomography, we have produced 4D movies (i.e., 3D + time) of up to 30,000 bubbles. After a transient regime, the successive images look alike, except that the average bubble size increases as the square root of time: This scaling state is the long sought self-similar growth regime. The bubble size and face-number distributions in this regime are compared with experimental distributions for grains in crystals and with numerical simulations of foams. PMID:20867343

  4. Water use regimes: Characterizing direct human interaction with hydrologic systems

    NASA Astrophysics Data System (ADS)

    Weiskel, Peter K.; Vogel, Richard M.; Steeves, Peter A.; Zarriello, Philip J.; Desimone, Leslie A.; Ries, Kernell G.

    2007-04-01

    The sustainability of human water use practices is a rapidly growing concern in the United States and around the world. To better characterize direct human interaction with hydrologic systems (stream basins and aquifers), we introduce the concept of the water use regime. Unlike scalar indicators of anthropogenic hydrologic stress in the literature, the water use regime is a two-dimensional, vector indicator that can be depicted on simple x-y plots of normalized human withdrawals (hout) versus normalized human return flows (hin). Four end-member regimes, natural-flow-dominated (undeveloped), human-flow-dominated (churned), withdrawal-dominated (depleted), and return-flow-dominated (surcharged), are defined in relation to limiting values of hout and hin. For illustration, the water use regimes of 19 diverse hydrologic systems are plotted and interpreted. Several of these systems, including the Yellow River Basin, China, and the California Central Valley Aquifer, are shown to approach particular end-member regimes. Spatial and temporal regime variations, both seasonal and long-term, are depicted. Practical issues of data availability and regime uncertainty are addressed in relation to the statistical properties of the ratio estimators hout and hin. The water use regime is shown to be a useful tool for comparative water resources assessment and for describing both historic and alternative future pathways of water resource development at a range of scales.

  5. Water use regimes: Characterizing direct human interaction with hydrologic systems

    USGS Publications Warehouse

    Weiskel, P.K.; Vogel, R.M.; Steeves, P.A.; Zarriello, P.J.; DeSimone, L.A.; Ries, Kernell G., III

    2007-01-01

    [1] The sustainability of human water use practices is a rapidly growing concern in the United States and around the world. To better characterize direct human interaction with hydrologic systems (stream basins and aquifers), we introduce the concept of the water use regime. Unlike scalar indicators of anthropogenic hydrologic stress in the literature, the water use regime is a two-dimensional, vector indicator that can be depicted on simple x-y plots of normalized human withdrawals (hout) versus normalized human return flows (hin). Four end-member regimes, natural-flow-dominated (undeveloped), human-flow-dominated (churned), withdrawal-dominated (depleted), and return-flow-dominated (surcharged), are defined in relation to limiting values of hout and hin. For illustration, the water use regimes of 19 diverse hydrologic systems are plotted and interpreted. Several of these systems, including the Yellow River Basin, China, and the California Central Valley Aquifer, are shown to approach particular end-member regimes. Spatial and temporal regime variations, both seasonal and long-term, are depicted. Practical issues of data availability and regime uncertainty are addressed in relation to the statistical properties of the ratio estimators hout and hin. The water use regime is shown to be a useful tool for comparative water resources assessment and for describing both historic and alternative future pathways of water resource development at a range of scales. Copyright 2007 by the American Geophysical Union.

  6. An extended fractal growth regime in the diffusion limited aggregation including edge diffusion

    NASA Astrophysics Data System (ADS)

    Ghosh, Aritra; Batabyal, R.; Das, G. P.; Dev, B. N.

    2016-01-01

    We have investigated on-lattice diffusion limited aggregation (DLA) involving edge diffusion and compared the results with the standard DLA model. For both cases, we observe the existence of a crossover from the fractal to the compact regime as a function of sticking coefficient. However, our modified DLA model including edge diffusion shows an extended fractal growth regime like an earlier theoretical result using realistic growth models and physical parameters [Zhang et al., Phys. Rev. Lett. 73 (1994) 1829]. While the results of Zhang et al. showed the existence of the extended fractal growth regime only on triangular but not on square lattices, we find its existence on the square lattice. There is experimental evidence of this growth regime on a square lattice. The standard DLA model cannot characterize fractal morphology as the fractal dimension (Hausdorff dimension, DH) is insensitive to morphology. It also predicts DH = DP (the perimeter dimension). For the usual fractal structures, observed in growth experiments on surfaces, the perimeter dimension can differ significantly (DH ≠ DP) depending on the morphology. Our modified DLA model shows minor sensitivity to this difference.

  7. Plasma confinement regimes and collective modes characterizing them

    SciTech Connect

    Coppi, B.; Zhou, T.

    2012-10-15

    A unified theory is presented for the modes that are excited at the edge of the plasma column and are important signatures of the advanced confinement regimes into which magnetically confined plasmas can be driven. In particular, the so-called EDA H-Regime, the Elmy H-Regime, and the I-Regime are considered. The modes that are identified theoretically have characteristics that are consistent with or have anticipated those of the modes observed experimentally for each of the investigated regimes. The phase velocities, the produced transport processes, the frequencies, the wavelengths, and the consistency with the direction of spontaneous rotation are the factors considered for comparison with the relevant experiments. The quasi-coherent mode [I. Cziegler, Ph.D. dissertation, Massachusetts Institute of Technology, Cambridge, MA, 2011] that is present in the EDA H-Regime has a phase velocity in the direction of the ion diamagnetic velocity in the plasma reference frame. Consequently, this is identified as a ballooning mode near finite Larmor radius marginal stability involving the effects of transverse ion viscosity and other dissipative effects. In this regime, impurities are driven outward by the combined effects of the local temperature gradients of the impurities and their thermal conductivity, while in the Elmy H-Regime impurities are driven toward the center of the plasma column. In the I-Regimes, the excited 'Heavy Particle' modes [B. Coppi and T. Zhou, Phys. Plasmas 19, 012302 (2012); Phys. Lett. A 375, 2916 (2011)] are not of the ballooning kind and are shown to expel the impurities toward the plasma edge in the presence of significant fluctuations. These modes can have a finite frequency of oscillation with a phase velocity in the direction of the electron diamagnetic velocity or they can be nearly purely growing, explaining why there are I-Regimes where fluctuations are not observed. Instead, the modes considered for the Elmy H-Regime are of the ballooning

  8. Importance of characterizing growth trajectories

    PubMed Central

    Regnault, Nolwenn; Gillman, Matthew W

    2016-01-01

    In the era of the obesity epidemic in children, characterizing childhood growth trajectories (weight, height or BMI/ weight-for-length) is becoming essential for surveillance. Clinicians routinely use growth curves to identify abnormal growth trajectories. Clinical epidemiologists use growth trajectories for different purposes. They are interested in the determinants of growth but also in the consequences of certain patterns of growth on later health and diseases. Characterizing growth trajectories is also necessary if one wants to predict future growth based on past growth and might be useful in the future to compare the anticipated impact of various interventions. PMID:25413648

  9. Evaluating and optimizing horticultural regimes in space plant growth facilities

    NASA Technical Reports Server (NTRS)

    Berkovich, Y. A.; Chetirkin, P. V.; Wheeler, R. M.; Sager, J. C.

    2004-01-01

    In designing innovative space plant growth facilities (SPGF) for long duration space flight, various limitations must be addressed including onboard resources: volume, energy consumption, heat transfer and crew labor expenditure. The required accuracy in evaluating on board resources by using the equivalent mass methodology and applying it to the design of such facilities is not precise. This is due to the uncertainty of the structure and not completely understanding the properties of all associated hardware, including the technology in these systems. We present a simple criteria of optimization for horticultural regimes in SPGF: Qmax = max [M x (EBI)2/(V x E x T], where M is the crop harvest in terms of total dry biomass in the plant growth system; EBI is the edible biomass index (harvest index), V is volume occupied by the crop; E is the crop light energy supply during growth; T is the crop growth duration. The criterion reflects directly on the consumption of onboard resources for crop production. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  10. Characterization of diffusion processes: Normal and anomalous regimes

    NASA Astrophysics Data System (ADS)

    Alves, Samuel B.; de Oliveira, Gilson F.; de Oliveira, Luimar C.; Passerat de Silans, Thierry; Chevrollier, Martine; Oriá, Marcos; de S. Cavalcante, Hugo L. D.

    2016-04-01

    Many man-made and natural processes involve the diffusion of microscopic particles subject to random or chaotic, random-like movements. Besides the normal diffusion characterized by a Gaussian probability density function, whose variance increases linearly in time, so-called anomalous-diffusion regimes can also take place. They are characterized by a variance growing slower (subdiffusive) or faster (superdiffusive) than normal. In fact, many different underlying processes can lead to anomalous diffusion, with qualitative differences between mechanisms producing subdiffusion and mechanisms resulting in superdiffusion. Thus, a general description, encompassing all three regimes and where the specific mechanisms of each system are not explicit, is desirable. Here, our goal is to present a simple method of data analysis that enables one to characterize a model-less diffusion process from data observation, by observing the temporal evolution of the particle spread. To generate diffusive processes in different regimes, we use a Monte-Carlo routine in which both the step-size and the time-delay of the diffusing particles follow Pareto (inverse-power law) distributions, with either finite or diverging statistical momenta. We discuss on the application of this method to real systems.

  11. Small Seed Black Hole Growth in Various Accretion Regimes

    NASA Astrophysics Data System (ADS)

    Gerling-Dunsmore, Hannalore J.; Hopkins, Philip F.

    2016-03-01

    Observational evidence indicates a population of super massive black holes (SMBHs) (~109 -1010M⊙) formed within 1 Gyr after the Big Bang. One proposed means of SMBH formation is accretion onto small seed black holes (BHs) (~ 100M⊙). However, the existence of SMBHs within 1 Gyr requires rapid growth, but conventional models of accretion fail to grow the seed BHs quickly enough. Super Eddington accretion (Ṁ >ṀEddington) may aid in improving growth efficiency. We study small seed BH growth via accretion in 3D, using the magneto-hydrodynamics+gravity code GIZMO. In particular, we consider a BH in a high density turbulent star-forming cloud, and ask whether or not the BH can capture sufficient gas to grow rapidly. We consider both Eddington-limited and super Eddington regimes, and resolve physics on scales from 0.1 pc to 1 kpc while including detailed models for stellar feedback physics, including stellar winds, supernovae, radiation pressure, and photo-ionization. We present results on the viability of different small seed BHs growing into SMBH candidates.

  12. Regime switch in karstic caves atmosphere; possible consequence on annual speleothem growth.

    NASA Astrophysics Data System (ADS)

    Bourges, F.; Genthon, P.; Mangin, A.; D'Hulst, D.

    2005-12-01

    Speleothem are usually considered as records of past climate, and are supposed to present annual growth rings. Yet, they grow inside caves that benefit from very stable environment. However, Bourges et al. 2001, have shown that the atmosphere of Aven d'Orgnac (South East France), was characterized by drop of CO2 concentration and 222Rn activity at the end of autumn and presented each year the succession of a winter and a summer regime. Temperature data are now used to constrain the climate of this cave system. Our data consist in 5 years monitoring with 0.01°C accuracy, three short thermal profiling campaigns, and sparser data gathered in different French painted caves. Near the opening of Aven d'Orgnac, the Salle de Jolys room records each year at the end of autumn the onset of the winter regime that is shown to be triggered by the inverse density stratification induced by the decrease of the outside night temperature. Comparison of summer and winter vertical temperature profiles point to a thermoconvective destabilization of this room atmosphere, involving the downward flow of cold outside bearing air near the cave floor during winter nights. The winter regime propagates then stepwise inside the Aven d'Orgnac cave system. In Salle Plane, which is situated more than one kilometer away from the entrance, the winter regime has never been observed. Our thermal profiling experiment shows there low amplitude (0.03°C) temperature changes, with major daily and half daily components, that are strongly correlated with the pressure first time derivative. Comparison with temperature records from other rooms of the Aven d'Orgnac cave system and with other caves monitored by our team suggest that a strong correlation between temperature changes and the pressure first time derivative could be considered as a clue to the confined character of a given cave room. We propose therefore that the Aven d'Orgnac cave system could be divided in two parts : the open system, where the

  13. Regime Switching in the Latent Growth Curve Mixture Model

    ERIC Educational Resources Information Center

    Dolan, Conor V.; Schmittmann, Verena D.; Lubke, Gitta H.; Neale, Michael C.

    2005-01-01

    A linear latent growth curve mixture model is presented which includes switching between growth curves. Switching is accommodated by means of a Markov transition model. The model is formulated with switching as a highly constrained multivariate mixture model and is fitted using the freely available Mx program. The model is illustrated by analyzing…

  14. Phase-field modeling of submonolayer growth with the modulated nucleation regime

    NASA Astrophysics Data System (ADS)

    Dong, X. L.; Xing, H.; Chen, C. L.; Wang, J. Y.; Jin, K. X.

    2015-10-01

    In this letter, we perform the phase-field simulations to investigate nucleation regime of submonolayer growth via a quantified nucleation term. Results show that the nucleation related kinetic coefficients have changed the density of islands and critical sizes to modulate the nucleation regime. The scaling behavior of the island density can be agreed with the classical theory only when effects of modulations have been quantified. We expect to produce the quantitative descriptions of nucleation for submonolayer growth in phase-field models.

  15. Toward a Physical Characterization of Raindrop Collision Outcome Regimes

    NASA Technical Reports Server (NTRS)

    Testik, F. Y.; Barros, Ana P.; Bilven, Francis L.

    2011-01-01

    A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.

  16. Unveiling the Hard Anodization Regime of Aluminum: Insight into Nanopores Self-Organization and Growth Mechanism.

    PubMed

    Vega, Víctor; García, Javier; Montero-Moreno, Josep M; Hernando, Blanca; Bachmann, Julien; Prida, Víctor M; Nielsch, Kornelius

    2015-12-30

    Pores growth mechanism and their self-ordering conditions are investigated for nanoporous alumina membranes synthesized by hard anodization (HA) of Al in a broad range of anodic conditions, covering oxalic acid electrolytes with concentrations from 0.300 M down to 0.075 M and potentiostatic anodization voltages between 120 and 225 V. The use of linear sweep voltammetry (LSV) and scanning and transmission electron microscopy, together with image analysis techniques allow one to characterize the intrinsic nature of the HA regime. HA of aluminum is explained on the basis of a phenomenological model taking into account the role of oxalate ions and their limited diffusion through alumina nanochannels from a bulk electrolyte. The depletion of oxalate ions at the bottom of the pores causes an increased growth of the alumina barrier layer at the oxide/electrolyte interface. Furthermore, an innovative method has been developed for the determination of the HA conditions leading to self-ordered pore growth in any given electrolyte, thus allowing one to extend the available range of interpore distances of the highly ordered hexagonal pore arrangement in a wide range of 240-507 nm, while keeping small pore diameters of 50-60 nm. PMID:26646814

  17. Fatigue crack growth in the highly plastic regime

    SciTech Connect

    Kim, K.S.; Baik, Y.M.

    1997-12-31

    This paper evaluates the performance of {Delta}J{sup {star}}, {Delta}J[superscript karet] and {Delta}K as fracture parameters for center-cracked plate specimens of Alloy 718 under R{sub {sigma}} = 0, nominally elastic and plastic loading at elevated temperatures. The parameters {Delta}J{sup {star}} and {Delta}J[superscript caret] are computed from the results of an elastic-plastic finite element analysis of crack growth. At 538 C the results show, in contrast to the previous results of R{sup {var_epsilon}} = {minus}1 strain control tests, that the correlation of crack growth rates with {Delta}J{sup {star}} or {Delta}J[superscript caret] deviates from the relation of the Paris law type while {Delta}K gives a satisfactory correlation. The correlation at 649 C is poor for all three parameters. The finite element analysis shows that the crack closing behavior diminishes and eventually disappears as the crack tip plasticity increases due to crack growth or increased applied stress.

  18. Bunch self-focusing regime of laser wakefield acceleration with reduced emittance growth.

    PubMed

    Reitsma, A J W; Goloviznin, V V; Kamp, L P J; Schep, T J

    2002-01-01

    A new regime of laser wakefield acceleration of an injected electron bunch is described. In this regime, the bunch charge is so high that the bunch wakefields play an important role in the bunch dynamics. In particular, the transverse bunch wakefield induces a strong self-focusing that suppresses the transverse emittance growth arising from misalignment errors. The decelerating longitudinal bunch wakefield, however, is not so strong that it completely cancels the accelerating laser wakefield. In fact, the induced energy spread can be compensated by exploiting phase slippage effects. These features make the new regime interesting for high beam quality laser wakefield acceleration. PMID:11800957

  19. Ecosystem regime shifts have not affected growth and survivorship of eastern Beaufort Sea belugas.

    PubMed

    Luque, Sebastián P; Ferguson, Steven H

    2009-05-01

    Large-scale ocean-atmosphere physical dynamics can have profound impacts on the structure and organization of marine ecosystems. These changes have been termed "regime shifts", and five different episodes have been detected in the North Pacific Ocean, with concurrent changes also occurring in the Bering and Beaufort Seas. Belugas from the Eastern Beaufort Sea (EBS) use the Bering Sea during winter and the Beaufort Sea during summer, yet the potential effects of regime shifts on belugas have not been assessed. We investigated whether body size and survivorship of EBS belugas harvested in the Mackenzie River delta region between 1993 and 2003 have been affected by previous purported regime shifts in the North Pacific. Residuals from the relationship between body length and age were calculated and compared among belugas born between 1932 and 1989. Residual body size was not significantly related to birth year for any regime, nor to the age group individuals belonged to during any regime. The percentage deviation in number of belugas born in any given year that survived to be included in the hunt (survivorship) did not show any significant trend within or between regimes. Accounting for lags of 1-5 years did not reveal any evidence of delayed effects. Furthermore, neither population index was significantly related to changes in major climatic variables that precede regime shifts. Our results suggest that EBS beluga body size and survivorship have not been affected by the major regime shifts of the North Pacific and the adjacent Bering and Beaufort Seas. EBS belugas may have been able to modify their diet without compromising their growth and survivorship. Diet and reproductive analyses over large and small time scales can help understand the mechanisms enabling belugas to avoid significant growth and reproductive effects of past regime shifts. PMID:19229560

  20. Retarding the growth of the Rosensweig instability unveils a new scaling regime

    NASA Astrophysics Data System (ADS)

    Lange, Adrian; Gollwitzer, Christian; Maretzki, Robin; Rehberg, Ingo; Richter, Reinhard

    2016-04-01

    Using a highly viscous magnetic fluid, the dynamics in the aftermath of the Rosensweig instability can be slowed down by more than 2000 times. In this way we expand the regime where the growth rate is predicted to scale linearly with the bifurcation parameter by six orders of magnitude, while this regime is tiny for standard ferrofluids and cannot be resolved experimentally there. We measure the growth of the pattern by means of a two-dimensional imaging technique, and find that the slopes of the growth and decay rates are not the same—a qualitative discrepancy with respect to the theoretical predictions. We solve this discrepancy by taking into account a viscosity which is assumed to be different for the growth and decay. This may be a consequence of the measured shear thinning of the ferrofluid.

  1. Retarding the growth of the Rosensweig instability unveils a new scaling regime.

    PubMed

    Lange, Adrian; Gollwitzer, Christian; Maretzki, Robin; Rehberg, Ingo; Richter, Reinhard

    2016-04-01

    Using a highly viscous magnetic fluid, the dynamics in the aftermath of the Rosensweig instability can be slowed down by more than 2000 times. In this way we expand the regime where the growth rate is predicted to scale linearly with the bifurcation parameter by six orders of magnitude, while this regime is tiny for standard ferrofluids and cannot be resolved experimentally there. We measure the growth of the pattern by means of a two-dimensional imaging technique, and find that the slopes of the growth and decay rates are not the same-a qualitative discrepancy with respect to the theoretical predictions. We solve this discrepancy by taking into account a viscosity which is assumed to be different for the growth and decay. This may be a consequence of the measured shear thinning of the ferrofluid. PMID:27176389

  2. Equilibrating dynamics in quenched Bose gases: Characterizing multiple time regimes

    NASA Astrophysics Data System (ADS)

    Rançon, A.; Levin, K.

    2014-08-01

    We address the physics of equilibration in ultracold atomic gases following a quench of the interaction parameter. Our work is based on a bath model which generates damping of the bosonic excitations. We illustrate this dissipative behavior through the momentum distribution of the excitations nk, observing that larger k modes have shorter relaxation times τ (k); they will equilibrate faster, as has been claimed in recent experimental work. We identify three time regimes. At short times nk exhibits oscillations; these are damped out at intermediate times where the system appears to be in a false or slowly converging equilibrium. Finally, at longer times, full equilibration occurs. This false equilibrium is, importantly, associated with the k dependence in τ (k) and has implications for experiment.

  3. Geographic variation in Pacific herring growth in response to regime shifts in the North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Ito, Shin-ichi; Rose, Kenneth A.; Megrey, Bernard A.; Schweigert, Jake; Hay, Douglas; Werner, Francisco E.; Aita, Maki Noguchi

    2015-11-01

    Pacific herring populations at eight North Pacific Rim locations were simulated to compare basin-wide geographic variations in age-specific growth due to environmental influences on marine productivity and population-specific responses to regime shifts. Temperature and zooplankton abundance from a three-dimensional lower-trophic ecosystem model (NEMURO: North Pacific Ecosystem Model for Understanding Regional Oceanography) simulation from 1948 to 2002 were used as inputs to a herring bioenergetics growth model. Herring populations from California, the west coast of Vancouver Island (WCVI), Prince William Sound (PWS), Togiak Alaska, the western Bering Sea (WBS), the Sea of Okhotsk (SO), Sakhalin, and Peter the Great Bay (PGB) were examined. The half-saturation coefficients of herring feeding were calibrated to climatological conditions at each of the eight locations to reproduce averaged size-at-age data. The depth of averaging used for water temperature and zooplankton, and the maximum consumption rate parameter, were made specific to each location. Using the calibrated half-saturation coefficients, the 1948-2002 period was then simulated using daily values of water temperature and zooplankton densities interpolated from monthly model output. To detect regime shifts in simulated temperatures, zooplankton and herring growth rates, we applied sequential t-test analyses on the 54 years of hindcast simulation values. The detected shifts of herring age-5 growth showed closest match (69%) to the regime shift years (1957/58, 1970/71, 1976/77, 1988/89, 1998/99). We explored relationships among locations using cluster and principal component analyses. The first principal component of water temperature showed good correspondence to the Pacific Decadal Oscillation and all zooplankton groups showed a pan-Pacific decrease after the 1976/77 regime shift. However, the first principal component of herring growth rate showed decreased growth at the SO, PWS, WCVI and California

  4. Regimes of radial growth for Ga-catalyzed GaAs nanowires

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.; Berdnikov, Y.; Sibirev, N. V.

    2016-07-01

    We present a non-stationary growth model of Ga-catalyzed GaAs nanowires which is based on the two kinetic equations for the nanowire elongation rate and a time-dependent base radius of the droplet. We show that self-catalyzed nanowire growth is principally different from the Au-catalyzed one because a stationary droplet size cannot be maintained at all times. Close examination of the model enables us to separate different regimes of radial growth in which the droplet shrinks, inflates or converges to a certain stationary size as nanowires grow, depending on the initial droplet radius and the growth conditions. We also discuss some experimental data on the growth modes of Ga-catalyzed GaAs nanowires from the viewpoint of the obtained results.

  5. Characterization of stock market regimes by data compression

    NASA Astrophysics Data System (ADS)

    Vogel, Eugenio E.; Saravia, Gonzalo

    2011-03-01

    It has been shown that data compression can characterize magnetic phases (Physica A 388 (2009) 4075). In the introduction of this presentation we briefly review this result. We then go onto introducing a new data compressor (wlzip) developed by us to optimize recognition of meaningful patterns in the compressing procedure, yielding sharp transition curves at the magnetic critical temperatures. The advantages of the new compressor, such as better definition and tuning capabilities are presented. The rest of the talk consists of applying wlzip to the Chilean stock market along several months during 2010. The accumulated daily data allow to recognizing days with different types of activity. Moreover, the data recorded every minute allow to analyzing the ``present'' status of the stock market by applying wlzip to the data of the last hour or couple of hours. Possible extensions of the application of this technique to other fields are discussed. Partial support from Fondecyt 1100156, ICM and CEDENNA is acknowledged.

  6. Growth Laws and Self-Similar Growth Regimes of Coarsening Two-Dimensional Foams: Transition from Dry to Wet Limits

    NASA Astrophysics Data System (ADS)

    Fortuna, Ismael; Thomas, Gilberto L.; de Almeida, Rita M. C.; Graner, François

    2012-06-01

    We study the topology and geometry of two-dimensional coarsening foam with an arbitrary liquid fraction. To interpolate between the dry limit described by von Neumann’s law and the wet limit described by Marqusee’s equation, the relevant bubble characteristics are the Plateau border radius and a new variable: the effective number of sides. We propose an equation for the individual bubble growth rate as the weighted sum of the growth through bubble-bubble interfaces and through bubble-Plateau border interfaces. The resulting prediction is successfully tested, without an adjustable parameter, using extensive bidimensional Potts model simulations. The simulations also show that a self-similar growth regime is observed at any liquid fraction, and they also determine how the average size growth exponent, side number distribution, and relative size distribution interpolate between the extreme limits. Applications include concentrated emulsions, grains in polycrystals, and other domains with coarsening that is driven by curvature.

  7. Characterization of Inductively Coupled Plasmas in High Power, High Pressure Regime

    NASA Astrophysics Data System (ADS)

    Wang, Jun-Chieh; Kenney, Jason; Agarwal, Ankur; Nichols, Michael; Rogers, James; Rauf, Shahid

    2015-09-01

    Inductively coupled plasmas (ICP) are widely used in the microelectronic industry for thin film etching. ICPs have typically been operated at low gas pressures (<50 mTorr) and they have been well-characterized in this regime. Several applications requiring high etch rates (e.g., vertical NAND etch) have recently extended the use of ICPs to the high power (>4000 W) and high pressure (>100 mTorr) regime. ICP operation in this high-power, high-pressure regime imposes a tremendous challenge of achieving good plasma uniformity over large substrates. This necessitates a good theoretical understanding of the underlying physics, thorough experimental characterization, and more accurate numerical models for hardware design guidance. In this study, we will focus on the characterization of ICP in the high-power, high-pressure regime. Computational modeling is done using CRTRS, our in-house 2D/3D plasma model. The fluid plasma model is coupled to a circuit model to self-consistently account for the capacitive coupling from the coils that is expected to dominate in this operating regime. Properties of Ar plasma will be discussed and compared with experiments. The impact of critical operating parameters such as ICP power, pressure, flow rate, and current ratio (in multi-coil antenna structures) on plasma characteristics will be examined. Results in relevant processing gases will also be discussed.

  8. Shape transition of endotaxial islands growth from kinetically constrained to equilibrium regimes

    SciTech Connect

    Li, Zhi-Peng; Tok, Engsoon; Foo, Yonglim

    2013-09-01

    Graphical abstract: - Highlights: • All Fe{sub 13}Ge{sub 8} islands will grow into Ge(0 0 1) substrate at temperatures from 350 to 675 °C. • Shape transition occurred from kinetically constrained to equilibrium regime. • All endotaxial islands can be clarified into two types. • The mechanisms of endotaxial growth and shape transition have been rationalized. - Abstract: A comprehensive study of Fe grown on Ge(0 0 1) substrates has been conducted at elevated temperatures, ranging from 350 to 675 °C. All iron germinide islands, with the same Fe{sub 13}Ge{sub 8} phase, grow into the Ge substrate with the same epitaxial relationship. Shape transition occurs from small square islands (low temperatures), to elongated orthogonal islands or orthogonal nanowires (intermediate temperatures), and then finally to large square orthogonal islands (high temperatures). According to both transmission electron microscopy (TEM) and atomic force microscopy (AFM) investigations, all islands can be defined as either type-I or type-II. Type-I islands usually form at kinetically constrained growth regimes, like truncated pyramids. Type-II islands usually appear at equilibrium growth regimes forming a dome-like shape. Based on a simple semi-quantitative model, type-II islands have a lower total energy per volume than type-I, which is considered as the dominant mechanism for this type of shape transition. Moreover, this study not only elucidates details of endotaxial growth in the Fe–Ge system, but also suggests the possibility of controlled fabrication of temperature-dependent nanostructures, especially in materials with dissimilar crystal structures.

  9. Identifying crystallization- and incorporation-limited regimes during vapor-liquid-solid growth of Si nanowires.

    PubMed

    Pinion, Christopher W; Nenon, David P; Christesen, Joseph D; Cahoon, James F

    2014-06-24

    The vapor-liquid-solid (VLS) mechanism is widely used for the synthesis of semiconductor nanowires (NWs), yet several aspects of the mechanism are not fully understood. Here, we present comprehensive experimental measurements on the growth rate of Au-catalyzed Si NWs over a range of temperatures (365-480 °C), diameters (30-200 nm), and pressures (0.1-1.6 Torr SiH4). We develop a kinetic model of VLS growth that includes (1) Si incorporation into the liquid Au-Si catalyst, (2) Si evaporation from the catalyst surface, and (3) Si crystallization at the catalyst-NW interface. This simple model quantitatively explains growth rate data collected over more than 65 distinct synthetic conditions. Surprisingly, upon increasing the temperature and/or pressure, the analysis reveals an abrupt transition from a diameter-independent growth rate that is limited by incorporation to a diameter-dependent growth rate that is limited by crystallization. The identification of two distinct growth regimes provides insight into the synthetic conditions needed for specific NW-based technologies, and our kinetic model provides a straightforward framework for understanding VLS growth with a range of metal catalysts and semiconductor materials. PMID:24815744

  10. Wheat and Rice Growth Stages and Fertilization Regimes Alter Soil Bacterial Community Structure, But Not Diversity

    PubMed Central

    Wang, Jichen; Xue, Chao; Song, Yang; Wang, Lei; Huang, Qiwei; Shen, Qirong

    2016-01-01

    Maintaining soil fertility and the microbial communities that determine fertility is critical to sustainable agricultural strategies, and the use of different organic fertilizer (OF) regimes represents an important practice in attempts to preserve soil quality. However, little is known about the dynamic response of bacterial communities to fertilization regimes across crop growth stages. In this study, we examined microbial community structure and diversity across eight representative growth stages of wheat-rice rotation under four different fertilization treatments: no nitrogen fertilizer (NNF), chemical fertilizer (CF), organic–inorganic mixed fertilizer (OIMF), and OF. Quantitative PCR (QPCR) and high-throughput sequencing of bacterial 16S rRNA gene fragments revealed that growth stage as the best predictor of bacterial community abundance and structure. Additionally, bacterial community compositions differed between wheat and rice rotations. Relative to soils under wheat rotation, soils under rice rotation contained higher relative abundances (RA) of anaerobic and mesophilic microbes and lower RA of aerophilic microbes. With respect to fertilization regime, NNF plots had a higher abundance of nitrogen–fixing Cyanobacteria. OIMF had a lower abundance of ammonia-oxidizing Thaumarchaeota compared with CF. Application of chemical fertilizers (CF and OIMF treatments) significantly increased the abundance of some generally oligotrophic bacteria such those belonging to the Acidobacteria, while more copiotrophic of the phylum Proteobacteria increased with OF application. A high correlation coefficient was found when comparing RA of Acidobacteria based upon QPCR vs. sequence analysis, yet poor correlations were found for the α- and β- Proteobacteria, highlighting the caution required when interpreting these molecular data. In total, crop, fertilization scheme and plant developmental stage all influenced soil microbial community structure, but not total levels of

  11. Wheat and Rice Growth Stages and Fertilization Regimes Alter Soil Bacterial Community Structure, But Not Diversity.

    PubMed

    Wang, Jichen; Xue, Chao; Song, Yang; Wang, Lei; Huang, Qiwei; Shen, Qirong

    2016-01-01

    Maintaining soil fertility and the microbial communities that determine fertility is critical to sustainable agricultural strategies, and the use of different organic fertilizer (OF) regimes represents an important practice in attempts to preserve soil quality. However, little is known about the dynamic response of bacterial communities to fertilization regimes across crop growth stages. In this study, we examined microbial community structure and diversity across eight representative growth stages of wheat-rice rotation under four different fertilization treatments: no nitrogen fertilizer (NNF), chemical fertilizer (CF), organic-inorganic mixed fertilizer (OIMF), and OF. Quantitative PCR (QPCR) and high-throughput sequencing of bacterial 16S rRNA gene fragments revealed that growth stage as the best predictor of bacterial community abundance and structure. Additionally, bacterial community compositions differed between wheat and rice rotations. Relative to soils under wheat rotation, soils under rice rotation contained higher relative abundances (RA) of anaerobic and mesophilic microbes and lower RA of aerophilic microbes. With respect to fertilization regime, NNF plots had a higher abundance of nitrogen-fixing Cyanobacteria. OIMF had a lower abundance of ammonia-oxidizing Thaumarchaeota compared with CF. Application of chemical fertilizers (CF and OIMF treatments) significantly increased the abundance of some generally oligotrophic bacteria such those belonging to the Acidobacteria, while more copiotrophic of the phylum Proteobacteria increased with OF application. A high correlation coefficient was found when comparing RA of Acidobacteria based upon QPCR vs. sequence analysis, yet poor correlations were found for the α- and β- Proteobacteria, highlighting the caution required when interpreting these molecular data. In total, crop, fertilization scheme and plant developmental stage all influenced soil microbial community structure, but not total levels of alpha

  12. Modelling of salad plants growth and physiological status in vitamin space greenhouse during lighting regime optimization

    NASA Astrophysics Data System (ADS)

    Konovalova, Irina; Berkovich, Yuliy A.; Smolyanina, Svetlana; Erokhin, Alexei; Yakovleva, Olga; Lapach, Sergij; Radchenko, Stanislav; Znamenskii, Artem; Tarakanov, Ivan

    2016-07-01

    The efficiency of the photoautotrophic element as part of bio-engineering life-support systems is determined substantially by lighting regime. The artificial light regime optimization complexity results from the wide range of plant physiological functions controlled by light: trophic, informative, biosynthetical, etc. An average photosynthetic photon flux density (PPFD), light spectral composition and pulsed light effects on the crop growth and plant physiological status were studied in the multivariate experiment, including 16 independent experiments in 3 replicates. Chinese cabbage plants (Brassica chinensis L.), cultivar Vesnianka, were grown during 24 days in a climatic chamber under white and red light-emitting diodes (LEDs): photoperiod 24 h, PPFD from 260 to 500 µM/(m ^{2}*s), red light share in the spectrum varying from 33% to 73%, pulsed (pulse period from 30 to 501 µs) and non-pulsed lighting. The regressions of plant photosynthetic and biochemical indexes as well as the crop specific productivity in response to the selected parameters of lighting regime were calculated. Developed models of crop net photosynthesis and dark respiration revealed the most intense gas exchange area corresponding to PPFD level 450 - 500 µM/(m ^{2}*s) with red light share in the spectrum about 60% and the pulse length 30 µs with a pulse period from 300 to 400 µs. Shoot dry weight increased monotonically in response to the increasing PPFD and changed depending on the pulse period under stabilized PPFD level. An increase in ascorbic acid content in the shoot biomass was revealed when increasing red light share in spectrum from 33% to 73%. The lighting regime optimization criterion (Q) was designed for the vitamin space greenhouse as the maximum of a crop yield square on its ascorbic acid concentration, divided by the light energy consumption. The regression model of optimization criterion was constructed based on the experimental data. The analysis of the model made it

  13. Characterization of electron kinetics regime with electron energy probability functions in inductively coupled hydrogen plasmas

    NASA Astrophysics Data System (ADS)

    Kim, June Young; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-02-01

    Electron kinetics regime is characterized with the evolution of electron energy probability functions (EEPFs) in inductively coupled hydrogen plasmas. Measurements on EEPFs are carried out with a radio-frequency-compensated single Langmuir probe at the center of a planar-type hydrogen plasma driven by 13.56 MHz wave frequency. Measured EEPFs deviate considerably from the Maxwellian distribution only at relatively high pressures (15-40 mTorr), and the effective electron temperature steeply decreases as the gas pressure increases. Such evolution of the EEPF shapes with pressures is discussed in the consideration of the electron energy relaxation length and various characteristic frequencies. It is found that the EEPFs show locally depleted electron energy distribution where the electron-molecule vibrational collision frequency exceeds the electron-electron collision frequency at the local kinetics regime, while the measured EEPF is not dependent on the vibrational collision frequency at the non-local kinetics regime. Variation of the EEPF shape with distance from the heating region at the local kinetics regime is also well explained in the context of the energy relaxation length and electron-molecule collision frequencies. This study indicates that the control of electron energy distribution should be carried out in the consideration of electron kinetic regime depending on the energy relaxation length for various hydrogen plasma sources.

  14. Modular Growth in Bryozoans and the Inference of Pliocene Climate Regimes

    NASA Astrophysics Data System (ADS)

    Okamura, B.; O'Dea, A.; Knowles, T.; Clark, N.; Williams, M.

    2010-12-01

    We describe how variation in the modular growth of marine cheilostome bryozoans can be used to infer mean annual ranges in temperature (MART) through the application of the zooid-size MART technique (zs-MART) - an underutilised proxy for estimating seasonal temperature regimes in present-day and ancient environments. Inferences of temperature variation based on analyses of modular growth in bryozoans provide insights on both intra- and interannual environmental variation, and thereby enhance the climate records that are gleaned from foraminifers and other microfossils. The growing body of research to establish and utilise the zs-MART approach demonstrates its wide potential for gaining robust estimates of ancient temperature regimes, particularly when incorporated as part of a multi-proxy toolkit. We review how the zooid-size MART approach has enabled reconstruction of palaeoseasonality for the Pliocene across the North Atlantic, during the closure of the isthmus of Panama and in Antarctica and compare these data with those generated by other biological proxies and with output from GCMs.

  15. Feed and Feeding Regime Affect Growth Rate and Gonadosomatic Index of Adult Zebrafish (Danio Rerio)

    PubMed Central

    Law, Sheran Hiu Wan

    2013-01-01

    Abstract A 5-week study was conducted to evaluate commercially available Artemia, Ziegler zebrafish diet, and Calamac diet fed in five different feeding regimes on the growth and reproductive development of 7-month-old zebrafish. Zebrafish were fed to satiation three times daily during the normal work week and twice daily during the weekend and holidays. Zebrafish in dietary groups CCC (Calamac three times daily) and CCA (Calamac twice daily, Artemia once daily) had a significantly (p<0.05) greater weight gain and specific growth rate as compared to all other dietary groups. Male zebrafish in dietary group 5 had significantly larger gonadosomatic index (GSI) values than all other groups, while female zebrafish in dietary group CCC had significantly larger GSI values than all other groups. No differences in the fatty acid content of female gonads were detected. Zebrafish fed solely Artemia had the greatest weight loss and lowest GSI values. Preliminary evidence of protein sparing in zebrafish is reported. Collectively, this study sheds more light into the effects of the use of commercially available feeds and feeding regime on the rearing of zebrafish. PMID:23902461

  16. Numerical analysis of granular flows in a silo bed on flow regime characterization.

    PubMed

    Yang, Xingtuan; Gui, Nan; Tu, Jiyuan; Jiang, Shengyao

    2015-01-01

    The flow characteristics of a gravity-driven dense granular flow in a granular bed with a contracted drainage orifice are studied by using discrete element method and quantitative analysis. Three values of discharging rates, ranging from fast to slow dense flows, are investigated. Time variations and derivatives of mean forces and velocities, as well as their respective correlations, are analyzed to quantitatively depict the characteristics of granular flow as well as flow regime categorization. The auto-correlation functions, as well as their Fourier spectrums, are utilized to characterize the differences between the mechanisms of slow and fast granular flows. Finally, it is suggested that the flow regimes of slow and fast flows can be characterized by the kinetic and kinematic flow properties of particles. PMID:25793996

  17. Numerical Analysis of Granular Flows in a Silo Bed on Flow Regime Characterization

    PubMed Central

    Yang, Xingtuan; Gui, Nan; Tu, Jiyuan; Jiang, Shengyao

    2015-01-01

    The flow characteristics of a gravity-driven dense granular flow in a granular bed with a contracted drainage orifice are studied by using discrete element method and quantitative analysis. Three values of discharging rates, ranging from fast to slow dense flows, are investigated. Time variations and derivatives of mean forces and velocities, as well as their respective correlations, are analyzed to quantitatively depict the characteristics of granular flow as well as flow regime categorization. The auto-correlation functions, as well as their Fourier spectrums, are utilized to characterize the differences between the mechanisms of slow and fast granular flows. Finally, it is suggested that the flow regimes of slow and fast flows can be characterized by the kinetic and kinematic flow properties of particles. PMID:25793996

  18. Mesoscopic Impurities Expose a Nucleation-Limited Regime of Crystal Growth

    NASA Astrophysics Data System (ADS)

    Sleutel, Mike; Lutsko, James F.; Maes, Dominique; Van Driessche, Alexander E. S.

    2015-06-01

    Nanoscale self-assembly is naturally subject to impediments at the nanoscale. The recently developed ability to follow processes at the molecular level forces us to resolve older, coarse-grained concepts in terms of their molecular mechanisms. In this Letter, we highlight one such example. We present evidence based on experimental and simulation data that one of the cornerstones of crystal growth theory, the Cabrera-Vermilyea model of step advancement in the presence of impurities, is based on incomplete physics. We demonstrate that the piercing of an impurity fence by elementary steps is not solely determined by the Gibbs-Thomson effect, as assumed by Cabrera-Vermilyea. Our data show that for conditions leading up to growth cessation, step retardation is dominated by the formation of critically sized fluctuations. The growth recovery of steps is counter to what is typically assumed, not instantaneous. Our observations on mesoscopic impurities for lysozyme expose a nucleation-dominated regime of growth that has not been hitherto considered, where the system alternates between zero and near-pure velocity. The time spent by the system in arrest is the nucleation induction time required for the step to amass a supercritical fluctuation that pierces the impurity fence.

  19. Observation of Rayleigh-Taylor-instability growth in a plasma regime with magnetic and viscous stabilization

    NASA Astrophysics Data System (ADS)

    Adams, Colin

    2015-11-01

    Rayleigh-Taylor-instability (RTI) growth during the interaction between a high-Mach-number, unmagnetized plasma jet and a stagnated, magnetized plasma is observed in a regime where the growth of short-wavelength modes is influenced by plasma viscosity and magnetic fields. The time evolution of mode growth at the mostly planar interface is captured by a multi-frame fast camera. Interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to experimentally infer ni, Te, Z , acceleration, B -->, and ion viscosity in the vicinity of the evolving interface. As the instability grows, an evolution from mode wavelengths of ~ 1 . 7 cm to ~ 2 . 8 cm is observed. The growth time (~ 10 μs) and wavelength (~ 1 cm) of the observed modes agree with theoretical predictions computed from the experimentally inferred density (~1014 cm-3), deceleration (~109 m /s2), and magnetic field (~ 15 G in direction of wavevector). Furthermore, comparisons of experimental data with idealized magnetohydrodynamic simulations (which include a physical viscosity model) suggest that both magnetic and viscous stabilization contribute to the observed mode evolution. These data are relevant for benchmarking astrophysical and magneto-inertial-fusion-relevant computations of RTI. Supported by the LANL LDRD Program; PLX facility construction supported by OFES.

  20. Characterization of potential fire regimes: applying landscape ecology to fire management in Mexico

    NASA Astrophysics Data System (ADS)

    Jardel, E.; Alvarado, E.; Perez-Salicrup, D.; Morfín-Rios, J.

    2013-05-01

    Knowledge and understanding of fire regimes is fundamental to design sound fire management practices. The high ecosystem diversity of Mexico offers a great challenge to characterize the fire regime variation at the landscape level. A conceptual model was developed considering the main factors controlling fire regimes: climate and vegetation cover. We classified landscape units combining bioclimatic zones from the Holdridge life-zone system and actual vegetation cover. Since bioclimatic conditions control primary productivity and biomass accumulation (potential fuel), each landscape unit was considered as a fuel bed with a particular fire intensity and behavior potential. Climate is also a determinant factor of post-fire recovery rates of fuel beds, and climate seasonality (length of the dry and wet seasons) influences fire probability (available fuel and ignition efficiency). These two factors influence potential fire frequency. Potential fire severity can be inferred from fire frequency, fire intensity and behavior, and vegetation composition and structure. Based in the conceptual model, an exhaustive literature review and expert opinion, we developed rules to assign a potential fire regime (PFR) defined by frequency, intensity and severity (i.e. fire regime) to each bioclimatic-vegetation landscape unit. Three groups and eight types of potential fire regimes were identified. In Group A are fire-prone ecosystems with frequent low severity surface fires in grasslands (PFR type I) or forests with long dry season (II) and infrequent high-severity fires in chaparral (III), wet temperate forests (IV, fire restricted by humidity), and dry temperate forests (V, fire restricted by fuel recovery rate). Group B includes fire-reluctant ecosystems with very infrequent or occasional mixed severity surface fires limited by moisture in tropical rain forests (VI) or fuel availability in seasonally dry tropical forests (VII). Group C and PFR VIII include fire-free environments

  1. A Maturing Global Testing Regime Meets the World Economy: Test Scores and Economic Growth, 1960-2012

    ERIC Educational Resources Information Center

    Kamens, David H.

    2015-01-01

    This article considers the growth of the international testing regime. It discusses sources of growth and empirically examines two related sets of issues: (1) the stability of countries' achievement scores, and (2) the influence of those national scores on subsequent economic development over different time lags. The article suggests that…

  2. Coalescence-controlled and coalescence-free growth regimes during deposition of pulsed metal vapor fluxes on insulating surfaces

    SciTech Connect

    Lü, B.; Münger, E. P.; Sarakinos, K.

    2015-04-07

    The morphology and physical properties of thin films deposited by vapor condensation on solid surfaces are predominantly set by the processes of island nucleation, growth, and coalescence. When deposition is performed using pulsed vapor fluxes, three distinct nucleation regimes are known to exist depending on the temporal profile of the flux. These regimes can be accessed by tuning deposition conditions; however, their effect on film microstructure becomes marginal when coalescence sets in and erases morphological features obtained during nucleation. By preventing coalescence from being completed, these nucleation regimes can be used to control microstructure evolution and thus access a larger palette of film morphological features. Recently, we derived the quantitative criterion to stop coalescence during continuous metal vapor flux deposition on insulating surfaces—which typically yields 3-dimensional growth—by describing analytically the competition between island growth by atomic incorporation and the coalescence rate of islands [Lü et al., Appl. Phys. Lett. 105, 163107 (2014)]. Here, we develop the analytical framework for entering a coalescence-free growth regime for metal vapor deposition on insulating substrates using pulsed vapor fluxes, showing that there exist three distinct criteria for suppressing coalescence that correspond to the three nucleation regimes of pulsed vapor flux deposition. The theoretical framework developed herein is substantiated by kinetic Monte Carlo growth simulations. Our findings highlight the possibility of using atomistic nucleation theory for pulsed vapor deposition to control morphology of thin films beyond the point of island density saturation.

  3. Phosphorus acquisition and growth of Pinus ponderosa under different climate regimes

    SciTech Connect

    DeLucia, E.H.; Callaway, R.M.; Thomas, E.M.

    1995-06-01

    Ponderosa pine seedlings were grown with an organic P fertilizer in a factorial 2 temp (25 & 30 C) and 2 CO{sub 2} (350 & 700 {mu}l/l) design. Elevated CO{sub 2} stimulated growth and elevated CO{sub 2} and temp increased the specific absorption rate of P by ca. 30%. The percent infection by mycorrhizae increased with elevated CO{sub 2} but decreased with elevated temp. In contrast, the activity of root phosphatases was depressed in seedlings grown under elevated CO{sub 2} and temperature. Thus, there appears to be a functional tradeoff in the mechanisms of P acquisition in different climate regimes. Under current conditions root phosphatase activity is high and mycorrhizal infection is low. This reverses under simulated future conditions of elevated temp and CO{sub 2}. The concentration of soil oxalate also increased under elevated CO{sub 2}. This small organic acid, released by roots and fungi, chelates Ca, Fe, and Al in the soil thereby increasing the availability of inorganic P. Enhanced P acquisition and utilization under elevated CO{sub 2} and temp contributed to higher growth rates suggesting that ponderosa pine may overcome P limitations under future climate conditions.

  4. Characterization of magnetic reconnection in the high-energy-density regime

    NASA Astrophysics Data System (ADS)

    Qiao, B.; Xu, Z.; Chang, H. X.; Wu, S. Z.; Zhou, C. T.; Wang, X. G.; He, X. T.

    2015-11-01

    Magnetic reconnection (MR), breaking and reorganizing the topology of magnetic field dramatically, is a fundamental process observed in many space, laboratory and astrophysical plasmas. In this talk, we report recent investigations on characterization of magnetic reconnection (MR) in the high-energy-density (HED) regime, where the plasma inflow is strongly driven and the total thermal pressure is larger than the magnetic pressure (β > 1) . This extreme regime of MR occurs frequently in astrophysics and recent HED experiments. Comparing the particle-in-cell simulation results for the interactions of colliding laser-produced plasma bubbles with induced anti-parallel and parallel poloidal magnetic fields respectively, the consequences caused by MR are distinguished from those by plasma bubble collisions and two-fluid effects. It is found that the out-of-plane quadrupole magnetic field, bipolar poloidal electric field, plasma heating and even the out-of-plane electric field appear in both cases, which cannot be recognized as evidences of MR here as previously thought. The Lorentz-invariant scalar quantity De =γe \\Jdot ⇀ . (E ⇀ + v ⇀ × B ⇀) [γe = (1 -ve2 /c2)- 1 / 2 is the Lorentz factor] in the electron dissipation region is proposed as the key sign of MR occurrence in the HED regime.

  5. Analytical Characterization of the Electrospray Ion Source in the Nanoflow Regime

    SciTech Connect

    Marginean, Ioan; Kelly, Ryan T.; Prior, David C.; Lamarche, Brian L.; Tang, Keqi; Smith, Richard D.

    2008-09-01

    We provide a thorough characterization of the low-flow electrospray as an ionization source for mass spectrometry (MS) using solutions typical for reversed-phase liquid chromatography. As expected, the electrospray operating regime strongly affects the MS signal; however, contrary to conventional wisdom, the pulsating regime consistently offers better performance than the cone-jet regime in these experimental conditions. We explain this observation by a highly efficient ionization achieved by the pulsating electrospray at low flow rates, rendering the increased charge generated by a cone-jet electrospray detrimental for transmission from atmospheric pressure to vacuum through a heated capillary interface. Over a wide range of voltages, the pulsating electrospray provides a relatively constant MS signal intensity, which depends significantly on the distance between the emitter and the MS inlet. For cone-jet electrosprays the MS signal decreases slightly with increasing voltage, but the signal is less affected by the emitter-inlet distance. At flow rates up to 100 nL/min the MS signal increases with increasing flow rate due to the larger number of ions supplied into the gas phase. At flow rates greater than 100 nL/min, the signal reaches a plateau due to increasingly unsatisfactory ionization efficiency at larger flow rates.

  6. [Responses of Medicago sativa and Astragalus adsurgens seedlings growth and water use to soil moisture regime].

    PubMed

    Xu, Bingcheng; Shan, Lun; Li, Fengmin

    2005-12-01

    In the semi-arid area of Loess Plateau, seasonal drought often occurs during the vegetative stage of grass plants, leading to the subsequent serious reduction of their yield. Aimed to study the responses of the seedlings growth and water use of two perennial leguminous grasses Medicago sativa and Astragalus adsurgens to different soil moisture regimes, a pot experiment was installed with five treatments, i.e., adequate water supply (HW), moderate water stress (LW), soil drying gradually from HW (DHW) and LW (DLW), and refilling water to LW after soil drying from LW (RWL). The results showed that under HW, the seedlings of both M. sativa and A. adsurgens had the highest biomass and transpiration water use efficiency (TWUE), and M. sativa had a significantly higher biomass than A. adsurgens (P < 0.05). When the soil moisture content declined, M. sativa had a higher reduction rate in biomass and TWUE than A. adsurgens, and after the soil moisture regime changed from LW and DLW to RWL, the biomass of M. sativa and A. adsurgens was reduced by 47.8% and 27.9%, respectively, as compared to LW (P < 0.05). At the same time, the root/shoot ratio (R/S) of M. sativa and its water consumption per unit root increased significantly, while the TWUE decreased significantly (P < 0.05); but for A. adsurgens, its R/S decreased significantly (P < 0.05), while the TWUE and the water consumption per unit root had no significant change. PMID:16515181

  7. [Response of photosynthesis and growth to weak light regime in different Adzuki bean (Vigna angularis) varieties].

    PubMed

    Zou, Chang-ming; Wang, Yun-qing; Cao, Wei-dong; Liu, Ying; Zhang, Xiao-hong; Tang, Shan

    2015-12-01

    In order to determine the adaptability of Adzuki beans as the interplanting crops in fruit yards, field and pot experimental treatments with full natural light and weak light (48% of full natural light) regimes were conducted to test the shade tolerance and physiological responses of three Adzuki bean varieties including Funan green Vigna angularis (FGVA), early-mature black V. angularis (EBVA) and late-mature black V. angularis (LBVA). The leaf photosynthetic characteristic parameters, photosynthetic pigment contents and the activity of RuBPCase were measured during the first bloom stage. The response of growth to weak light was likewise studied. The results showed that the photosynthetic characteristic parameters, i.e., the maximum net photosynthetic rate, light saturation point and light compensation point of the three Adzuki bean varieties under the weak light stress changed differently. The weak light stress induced the reduction of net photosynthetic rate, water use efficiency and RuBPCase activity of the three Adzuki bean varieties significantly. The contents of chlorophyll a and chlorophyll b in leaves of FGVA increased significantly, while Chl a/b and carotenoid content in the leaves decreased significantly after shading. But the other two varieties did not change obviously in photosynthetic pigments content after shading. The weak light changed the growth of the three Adzuki bean varieties, such as decreasing dry matter yield and dry matter accumulation efficiency, reducing root nodule and root-shoot ratio, debasing leaves quantity and leaf area index. The first bloom stage and maturing stage of FGVA advanced, while that of EBVA delayed under weak light. However, flowers were not strong enough to seed for LBVA under the weak light. In conclusion, according to the photosynthetic characteristics changes after shading, as well as the growth status, we concluded that the shade tolerance of the three Adzuki beans was ranked as FGVA>EBVA>LBVA. PMID:27112006

  8. Space-Time Characterization of Laser Plasma Interactions in the Warm Dense Matter Regime

    SciTech Connect

    Cao, L F; Uschmann, I; Forster, E; Zamponi, F; Kampfer, T; Fuhrmann, A; Holl, A; Redmer, R; Toleikis, S; Tschentsher, T; Glenzer, S H

    2008-04-30

    Laser plasma interaction experiments have been performed using a fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. The electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were compared with hydrodynamic simulation. First results to characterize the plasma density and temperature as a function of space and time are obtained. This work aims to generate plasmas in the warm dense matter (WDM) regime at near solid-density in an ultra-fast laser target interaction process. Plasmas under these conditions can serve as targets to develop x-ray Thomson scattering as a plasma diagnostic tool, e.g., using the VUV free-electron laser (FLASH) at DESY Hamburg.

  9. Effects of plant growth substances on rooting of Hedychium spicatum under different temperature regimes.

    PubMed

    Giri, Dinesh; Tamta, Sushma

    2013-03-01

    Present study was carried out to develop a simple and efficient vegetative propagation protocol by applying various treatments to rhizome cuttings with different test solutions of auxins and phenolic compound. These were alpha-naphthalene acetic acid (NAA), Indole-3-butyric acid (IBA), Indole Acetic Acid (IAA), phloroglucinol and coumarin. The concentrations for each treatment were 10.0, 50.0 and 100.0 microM. After treatments the rhizome cuttings were planted in polybags containing forest soil and kept under different temperature regimes i.e., inside polyhose (at 20-25 degrees C), inside mist chamber (at 15-20 degrees C) and under nethouse (nursery condition, at 14-18 degrees C). The maximum rooting percentage (74.06%) was achieved at 20-25 degrees C (inside polyhouse) by applying 50.0 microM IBA. Inside poly house condition, the various developmental parameters showed better responses compare to other conditions. On the basis of present study emphasizes that the temperature play a crucial role in rooting and further growth of the plants in this species. By using this simple and significant conventional method of propagation we could be propagate this vulnerable medicinal and aromatic species at large scale for commercial purpose. PMID:24175432

  10. Pedestal Characterization and Stability of Small-ELM Regimes in NSTX

    SciTech Connect

    Sontag, Aaron C; Canik, John; Maingi, Rajesh; Manickam, J.; Snyder, P.; Bell, R. E.; Gerhardt, S.P.; Kubota, S.; LaBlanc, B. P.; Mueller, D.; Osborne, T.; Tritz, K.

    2010-01-01

    An instability near the plasma edge known as the edge harmonic oscillation (EHO) is thought to enable access to the ELM-free quiescent H-mode (QH-mode) in tokamaks, which is a highly desirable operational regime for ITER because of the avoidance of periodic ELM heat loads. The EHO has been hypothesized to be a saturated kink driven unstable by toroidal rotational shear that provides sufficient transport near the plasma edge to keep the edge plasma below the peeling-ballooning stability limit. NSTX has observed unstable modes with similar characteristics to the EHO coincident with transition to a small-ELM regime (called Type-V). These small ELMs do not have a measurable effect on the plasma stored energy (< 1%). Transition to this regime is associated with a downward biased plasma as evidenced by drsep < -5 mm. Soft x-ray emission indicates that these modes are localized just inside the pedestal and are correlated with increased density fluctuations in the pedestal as measured by microwave reflectometry. The lowest order mode rotates at the plasma rotation frequency, indicating n=1, and harmonics up to n=6 have been observed simultaneously with the n=1, as determined by the rotation frequency of the higher harmonics. Increased edge collisionality is required to access Type-V ELMs. Stability analysis during the observed modes indicates instability to n=1-3 with n=3 having the highest growth rate and unstable mode eigenfunctions peaked near the plasma edge. Discharges with Type-V and Type-I ELMs are both calculated to be on the peeling unstable side of the peeling ballooning stability curve, with the Type-V case at higher normalized pressure gradient.

  11. Effects of constant and cyclical thermal regimes on growth and feeding of juvenile cutthroat trout of variable sizes

    USGS Publications Warehouse

    Meeuwig, M.H.; Dunham, J.B.; Hayes, J.P.; Vinyard, G.L.

    2004-01-01

    The effects of constant (12, 18, and 24 A?C) and cyclical (daily variation of 15a??21 and 12a??24 A?C) thermal regimes on the growth and feeding of Lahontan cutthroat trout (Oncorhynchus clarki henshawi) of variable sizes were examined. Higher constant temperatures (i.e., 24 A?C) and more variable daily temperatures (i.e., 12a??24 A?C daily cycle) negatively affected growth rates. As fish mass increased (from 0.24 to 15.52 g) the effects of different thermal regimes on mass growth became more pronounced. Following 14 days exposure to the thermal regimes, feeding rates of individual fish were assessed during acute exposure (40 min) to test temperatures of 12, 18, and 24 A?C. Feeding rate was depressed during acute exposure to 24 A?C, but was not significantly affected by the preceding thermal regime. Our results indicate that even brief daily exposure to higher temperatures (e.g., 24 A?C) can have considerable sublethal effects on cutthroat trout, and that fish size should be considered when examining the effects of temperature.

  12. How do soil physical conditions for crop growth vary over time under established contrasting tillage regimes?

    NASA Astrophysics Data System (ADS)

    Hallett, Paul; Stobart, Ron; Valentine, Tracy; George, Timothy; Morris, Nathan; Newton, Adrian; McKenzie, Blair

    2014-05-01

    When plant breeders develop modern cereal varieties for the sustainable intensification of agriculture, insufficient thought is given to the impact of tillage on soil physical conditions for crop production. In earlier work, we demonstrated that barley varieties that perform best in ploughed soil (the approach traditionally used for breeding trials) were not the same as those performing best under shallow non-inversion or zero-tillage. We also found that the Quantitative Trait Loci (QTL) associated with improved phosphorus uptake, and hence useful for marker assisted breeding, were not robust between different tillage regimes. The impact of the soil environment had greater impact than the genetics in GxE interactions. It is obvious that soil tillage should be considered when breeding the next generation of crops. Tillage may also have important impacts on carbon storage, but we found that despite greater soil carbon at shallow depths under non-inversion tillage, the carbon stored throughout the soil profile was not affected by tillage. Studies on soil tillage impacts to crop productivity and soil quality are often performed in one season, on single sites that have had insufficient time to develop. Our current research explores multiple sites, on different soils, with temporal measurements of soil physical conditions under contrasting tillage regimes. We use the oldest established contemporary tillage experiments in the United Kingdom, with all sites sharing ploughed and shallow (7cm) non-inversion tillage treatments. In eastern Scotland (Mid Pilmore), the site also has zero tillage and deep ploughing (40 cm) treatments, and was established 11 years ago. In east England there are two sites, both also having a deep non-inversion tillage treatment, and they were established 6 (New Farm Systems) and 8 (STAR) years ago. We measure a range of crop and soil properties at sowing, one month after sowing and post-harvest, including rapid lab based assays that allow high

  13. SiGe nanowire growth and characterization

    NASA Astrophysics Data System (ADS)

    Qi, Cheng; Goncher, Gary; Solanki, Raj; Jordan, Jay

    2007-02-01

    Single-crystal SiGe nanowires were synthesized via the vapour-liquid-solid (VLS) growth mechanism using disilane and germane as precursor gases. We have investigated the effect of temperature, pressure, and the inlet gas ratio on the growth and stoichiometry of SixGe1-x nanowires. The nanowires were characterized using scanning and transmission electron microscopies and energy dispersive x-ray analysis. It was found that nanowires with a Si:Ge ratio of about 1 had smooth surfaces, whereas departure from this ratio led to rough surfaces. Electrical properties were then investigated by fabricating back-gated field effect transistors (using a focused ion beam system) where single SiGe nanowires served as the conduction channels. Gated conduction was observed although resistance in the undoped devices was high.

  14. SiGe nanowire growth and characterization.

    PubMed

    Qi, Cheng; Goncher, Gary; Solanki, Raj; Jordan, Jay

    2007-02-21

    Single-crystal SiGe nanowires were synthesized via the vapour-liquid-solid (VLS) growth mechanism using disilane and germane as precursor gases. We have investigated the effect of temperature, pressure, and the inlet gas ratio on the growth and stoichiometry of Si(x)Ge(1-x) nanowires. The nanowires were characterized using scanning and transmission electron microscopies and energy dispersive x-ray analysis. It was found that nanowires with a Si:Ge ratio of about 1 had smooth surfaces, whereas departure from this ratio led to rough surfaces. Electrical properties were then investigated by fabricating back-gated field effect transistors (using a focused ion beam system) where single SiGe nanowires served as the conduction channels. Gated conduction was observed although resistance in the undoped devices was high. PMID:21730497

  15. Crystal phase control in GaAs nanowires: opposing trends in the Ga- and As-limited growth regimes.

    PubMed

    Lehmann, Sebastian; Jacobsson, Daniel; Dick, Kimberly A

    2015-07-31

    Here we demonstrate the existence of two distinct regimes for tuning crystal structure in GaAs nanowires from zinc blende to wurtzite using a single process parameter: V/III-ratio, or variation of the group V precursor flow. Extensive previous studies have shown that crystal structure is sensitive to V/III-ratio, and even that it is possible to change structure entirely using this single parameter. However, an open question has remained about whether the observed dependencies are related to growth technique or types of precursors used. Specifically, opposite trends have been reported for molecular beam epitaxy (MBE) and metal organic vapour phase epitaxy (MOVPE): while wurtzite GaAs growth is reported for high nominal V/III-ratio in MBE, zinc blende GaAs is formed in MOVPE under apparently the same parameter change (increasing precursor V/III-ratio). Here we show that these observations are not necessarily contradictory, as it may first appear, by providing a consolidated picture covering all regimes in one MOVPE growth machine only. More precisely, we observe wurtzite formation for medium nominal V/III-ratios with a critical sensitivity to the balance between Ga and As supply. Slight deviations from wurtzite conditions will result in zinc blende formation for either low V/III-ratio in the As-limited regime or high V/III-ratio in the Ga-limited regime. Our observations strongly indicate that the applied growth conditions are the crucial ingredients for crystal structure control in GaAs nanowires rather than the growth technique or precursors used. PMID:26160888

  16. Characterization of the regional variability of flood regimes within the Omo-Gibe River Basin, Ethiopia

    NASA Astrophysics Data System (ADS)

    Yared, Adanech; Demissie, Solomon S.; Sivapalan, Murugesu; Viglione, Alberto; MacAlister, Charlotte

    2014-05-01

    Hydrological variability and seasonality is one of the Ethiopia's primary water resource management challenges. Variability is most obviously manifest in endemic, devastating droughts and floods. While the level of flooding is quite often extremely high and destroys human beings and property, in many cases flooding is of vital importance because the community benefits from flood recession agriculture. This is the case of the lower Omo plain whose agriculture is based on the regularity of the inundations due to flooding of the Omo Gibe River. The big flood in 2006, which caused death for more than 300 people and 2000 cattle, poses a dilemma. Flooding must be controlled and regulated in a way that the damages are reduced as much as possible but the flooding-related benefits are not lost. To this aim, characterization and understanding of hydrological variability of the Omo Gibe River basin is fundamental. The goal of this work is to extract the maximal amount of information on the hydrological variability and specially on the flooding regime from the few data available in the region. Because most of the basin is ungauged, hydrological information is reconstructed using the data from 9 gauged catchments. A daily water balance model has been developed, calibrated and validated for 9 gauged catchments and, subsequently, the parameters have been correlated to catchment characteristics in order to establish a functional relationship that allows to apply the model to ungauged catchments. Daily streamflow has been predicted for 15 ungauged catchments, which are assumed to comprehensively represent the hydrological variability of the Omo-Gibe River Basin. Even though both northern and southern catchments are affected by a strong seasonality of precipitation, with most of the rain falling in less than 3 months, most of the northern catchments are humid, while in the southern part of the Omo-Gibe River basin, the catchments are either humid, dry sub humid, semiarid or arid. As

  17. Salicornia strobilacea (Synonym of Halocnemum strobilaceum) Grown under Different Tidal Regimes Selects Rhizosphere Bacteria Capable of Promoting Plant Growth

    PubMed Central

    Marasco, Ramona; Mapelli, Francesca; Rolli, Eleonora; Mosqueira, Maria J.; Fusi, Marco; Bariselli, Paola; Reddy, Muppala; Cherif, Ameur; Tsiamis, George; Borin, Sara; Daffonchio, Daniele

    2016-01-01

    Halophytes classified under the common name of salicornia colonize salty and coastal environments across tidal inundation gradients. To unravel the role of tide-related regimes on the structure and functionality of root associated bacteria, the rhizospheric soil of Salicornia strobilacea (synonym of Halocnemum strobilaceum) plants was studied in a tidal zone of the coastline of Southern Tunisia. Although total counts of cultivable bacteria did not change in the rhizosphere of plants grown along a tidal gradient, significant differences were observed in the diversity of both the cultivable and uncultivable bacterial communities. This observation indicates that the tidal regime is contributing to the bacterial species selection in the rhizosphere. Despite the observed diversity in the bacterial community structure, the plant growth promoting (PGP) potential of cultivable rhizospheric bacteria, assessed through in vitro and in vivo tests, was equally distributed along the tidal gradient. Root colonization tests with selected strains proved that halophyte rhizospheric bacteria (i) stably colonize S. strobilacea rhizoplane and the plant shoot suggesting that they move from the root to the shoot and (ii) are capable of improving plant growth. The versatility in the root colonization, the overall PGP traits and the in vivo plant growth promotion under saline condition suggest that such beneficial activities likely take place naturally under a range of tidal regimes. PMID:27597846

  18. Salicornia strobilacea (Synonym of Halocnemum strobilaceum) Grown under Different Tidal Regimes Selects Rhizosphere Bacteria Capable of Promoting Plant Growth.

    PubMed

    Marasco, Ramona; Mapelli, Francesca; Rolli, Eleonora; Mosqueira, Maria J; Fusi, Marco; Bariselli, Paola; Reddy, Muppala; Cherif, Ameur; Tsiamis, George; Borin, Sara; Daffonchio, Daniele

    2016-01-01

    Halophytes classified under the common name of salicornia colonize salty and coastal environments across tidal inundation gradients. To unravel the role of tide-related regimes on the structure and functionality of root associated bacteria, the rhizospheric soil of Salicornia strobilacea (synonym of Halocnemum strobilaceum) plants was studied in a tidal zone of the coastline of Southern Tunisia. Although total counts of cultivable bacteria did not change in the rhizosphere of plants grown along a tidal gradient, significant differences were observed in the diversity of both the cultivable and uncultivable bacterial communities. This observation indicates that the tidal regime is contributing to the bacterial species selection in the rhizosphere. Despite the observed diversity in the bacterial community structure, the plant growth promoting (PGP) potential of cultivable rhizospheric bacteria, assessed through in vitro and in vivo tests, was equally distributed along the tidal gradient. Root colonization tests with selected strains proved that halophyte rhizospheric bacteria (i) stably colonize S. strobilacea rhizoplane and the plant shoot suggesting that they move from the root to the shoot and (ii) are capable of improving plant growth. The versatility in the root colonization, the overall PGP traits and the in vivo plant growth promotion under saline condition suggest that such beneficial activities likely take place naturally under a range of tidal regimes. PMID:27597846

  19. Process regime variability across growth faults in the Paleogene Lower Wilcox Guadalupe Delta, South Texas Gulf Coast

    NASA Astrophysics Data System (ADS)

    Olariu, Mariana I.; Ambrose, William A.

    2016-07-01

    The Wilcox Group in Texas is a 3000 m thick unit of clastic sediments deposited along the Gulf of Mexico coast during early Paleogene. This study integrates core facies analysis with subsurface well-log correlation to document the sedimentology and stratigraphy of the Lower Wilcox Guadalupe Delta. Core descriptions indicate a transition from wave- and tidally-influenced to wave-dominated deposition. Upward-coarsening facies successions contain current ripples, organic matter, low trace fossil abundance and low diversity, which suggest deposition in a fluvial prodelta to delta front environment. Heterolithic stratification with lenticular, wavy and flaser bedding indicate tidal influence. Pervasively bioturbated sandy mudstones and muddy sandstones with Cruziana ichnofacies and structureless sandstones with Ophiomorpha record deposition in wave-influenced deltas. Tidal channels truncate delta front deposits and display gradational upward-fining facies successions with basal lags and sandy tabular cross-beds passing into heterolithic tidal flats and biologically homogenized mudstones. Growth faults within the lower Wilcox control expanded thickness of sedimentary units (up to 4 times) on the downdip sides of faults. Increased local accommodation due to fault subsidence favors a stronger wave regime on the outer shelf due to unrestricted fetch and water depth. As the shoreline advances during deltaic progradation, successively more sediment is deposited in the downthrown depocenters and reworked along shore by wave processes, resulting in a thick sedimentary unit characterized by repeated stacking of shoreface sequences. Thick and laterally continuous clean sandstone successions in the downthrown compartments represent attractive hydrocarbon reservoirs. As a consequence of the wave dominance and increased accommodation, thick (tens of meters) sandstone-bodies with increased homogeneity and vertical permeability within the stacked shoreface successions are created.

  20. Growth and characterization of semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Philipose, Usha

    This thesis describes a catalytic growth approach to synthesize semiconductor nanowires with good control over their physical dimensions, chemical composition, and optical/electronic properties. Using the Vapour-Liquid-Solid growth mechanism, gold nanoclusters serve as the catalytic sites directing the growth of crystalline Zinc Selenide (ZnSe), Zinc Oxide (ZnO) and Zinc Sulphide (ZnS) nanowires with length of several microns and diameters varying from 15 nm to 100 nm. The morphology and properties of the nanowires were found to be strongly dependent on growth conditions. Optical characterization by photoluminescence spectroscopy show that the spectra is dominated by near band edge emission for low defect density nanowires in contrast to the high level of defect related emission from high defect density nanowires. The growth parameters were optimized leading to the synthesis of nanowires with minimum defect concentration. Electrical transport studies on an array of ZnSe nanowires confirm that there exists a non-uniform carrier distribution along the nanowires leading to 'super-linear' current-voltage behaviour with carrier mobilities comparable to that of bulk material. Photoconductivity measurements on ZnSe nanoribbons show that they are of good quality, enabling realization of a nanoscale photodetector with a peak efficiency of 43%. Spectral response of photoconductivity had a threshold character with edge corresponding to the ZnSe bandgap, which makes it an ideal candidate for blue and ultraviolet light detection. The effect of doping of these nanowires with transition elements such as manganese (Mn) has been studied. In this effort, the first successful attempt at synthesizing room temperature ferromagnetic nanowires has been realized. Above room temperature ferromagnetism has been observed for the first time in dilute Mn-doped crystalline ZnO nanowires. From the observed saturation magnetization, the magnetic moment per Mn atom is estimated to be in the range

  1. Novel Growth Regime of MDCK II Model Tissues on Soft Substrates

    PubMed Central

    Kaliman, Sara; Jayachandran, Christina; Rehfeldt, Florian; Smith, Ana-Sunčana

    2014-01-01

    It is well established that MDCK II cells grow in circular colonies that densify until contact inhibition takes place. Here, we show that this behavior is only typical for colonies developing on hard substrates and report a new growth phase of MDCK II cells on soft gels. At the onset, the new phase is characterized by small, three-dimensional droplets of cells attached to the substrate. When the contact area between the agglomerate and the substrate becomes sufficiently large, a very dense monolayer nucleates in the center of the colony. This monolayer, surrounded by a belt of three-dimensionally packed cells, has a well-defined structure, independent of time and cluster size, as well as a density that is twice the steady-state density found on hard substrates. To release stress in such dense packing, extrusions of viable cells take place several days after seeding. The extruded cells create second-generation clusters, as evidenced by an archipelago of aggregates found in a vicinity of mother colonies, which points to a mechanically regulated migratory behavior. PMID:24703316

  2. Novel growth regime of MDCK II model tissues on soft substrates.

    PubMed

    Kaliman, Sara; Jayachandran, Christina; Rehfeldt, Florian; Smith, Ana-Sunčana

    2014-04-01

    It is well established that MDCK II cells grow in circular colonies that densify until contact inhibition takes place. Here, we show that this behavior is only typical for colonies developing on hard substrates and report a new growth phase of MDCK II cells on soft gels. At the onset, the new phase is characterized by small, three-dimensional droplets of cells attached to the substrate. When the contact area between the agglomerate and the substrate becomes sufficiently large, a very dense monolayer nucleates in the center of the colony. This monolayer, surrounded by a belt of three-dimensionally packed cells, has a well-defined structure, independent of time and cluster size, as well as a density that is twice the steady-state density found on hard substrates. To release stress in such dense packing, extrusions of viable cells take place several days after seeding. The extruded cells create second-generation clusters, as evidenced by an archipelago of aggregates found in a vicinity of mother colonies, which points to a mechanically regulated migratory behavior. PMID:24703316

  3. Characterization of the surface properties of wheat spikelet components grown under different regimes and the biocontrol yeast Cryptococcus flavescens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The physicochemical surfaces properties of wheat (Triticum aestivum L) spikelet components have been characterized under different environmental growing regimes. Wheat samples grown in a greenhouse environment were compared with samples produced in the field for two wheat cultivars (Freedom and Pion...

  4. Yield and growth characteristics for cotton under various irrigation regimes on sandy soil.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An irrigation experiment was set up to apply water to cotton at six different rates ranging from 33% to 144% of normal, with hopes of identifying the regime that produces maximum yield. Two cultivars, Acala Maxxa and Acala PhytoGen-72 were planted on sandy soil and irrigated daily with a highly effi...

  5. The effect of different flow regimes on the growth and metabolic rates of the scleractinian coral Galaxea fascicularis

    NASA Astrophysics Data System (ADS)

    Schutter, M.; Crocker, J.; Paijmans, A.; Janse, M.; Osinga, R.; Verreth, A. J.; Wijffels, R. H.

    2010-09-01

    To study the effect of water flow on coral growth, four series of ten coral nubbins of Galaxea fascicularis were exposed to four different flow regimes (0, 10, 20, and 25 cm s-1, bidirectional flow) for 42 weeks. Buoyant weight, surface area, and polyp number were measured at regular intervals. Net photosynthesis and dark respiration were measured at the corresponding flow speeds, and daily amount of photosynthetic carbon left for coral growth was calculated. Finally, skeletal density and CN content, chlorophyll concentration and dry weight of coral tissue were determined for each coral. Specific growth rate (in day-1) decreased with time in each flow treatment. Absence of flow resulted in significantly lower growth rates. Average specific growth rate calculated over the entire experiment was not significantly different between 10 and 20 cm s-1, while it was significantly higher at 25 cm s-1. From 10 to 25 cm s-1, average net photosynthetic rate decreased and average dark respiration rate did not change significantly. Scope for growth based on phototrophic carbon decreased with increasing flow. Growth was not positively correlated with either photosynthesis or respiration, or scope for growth. It is suggested that higher flow rates reduce the chance of disturbance of coral growth by competing algae or cyanobacteria, allowing corals to grow more readily with the maximum specific growth rate possible under the given environmental conditions. Notably, other effects of increased flow, such as increased respiratory rates and increased (in)organic nutrient uptake, might have been equally responsible for the increased growth of the corals in 25 cm s-1.

  6. Contrasted thermal regimes do not influence digestion and growth rates in a snake from a temperate climate.

    PubMed

    Michel, Catherine Louise; Bonnet, Xavier

    2010-01-01

    Temperature influences almost all life-history traits. For a period of 3 mo, we placed four groups of snakes under four contrasted thermal treatments: (1) a natural regime (NR), based on daily variations (24-h cycle); (2) an accelerated regime (AR), where the thermoperiod fluctuated rapidly (12-h cycle); (3) a slow regime (SR; 48-h cycle); and (4) a cool stable regime (ZR; no fluctuation). The mean temperature, set at 23°C, was identical for the four groups. For the first three groups (NR, AR, SR), ambient temperature fluctuated between 18°C and 28°C. Relative humidity and photoperiod were constant. We recorded feeding success, digestion efficiency, growth rate, activity, and ecdysis events. Differences between groups were expected because of varied exposure to the optimal temperatures, most notably in the ZR group, where the preferred body temperature for digestion (approximately 30°C) would not be reached. Surprisingly, there was no significant effect of the experimental treatment on feeding rate, digestion, body mass increase, and growth rate. Our results do not conform to the paradigm stipulating that maximal body temperature selected by ectotherms necessarily corresponds to the most efficient for resource assimilation and that temperature fluctuations are essential. We propose that increasing the digestive tract's performance through body-temperature elevation trades off against elevated (parasite) energy expenditure from the rest of the body. The main advantage of high body temperatures would be to reduce the amount of time necessary to assimilate prey rather than to improve the net mass gain during digestion. PMID:20969448

  7. Consequence of Continued Growth in the GEO and GEO Disposal Orbital Regimes

    NASA Technical Reports Server (NTRS)

    Johnson, Nicholas; Hanada, Toshiya; Krisko, Paula; Anz-Meador, Phillip

    2000-01-01

    To date more than 800 spacecraft, upper stages, and apogee kick motors are known to reside in geosynchronous and nearby orbits, including geosynchronous disposal orbits. An even larger number of debris greater than 10 em in diameter have been detected by U.S. and European groundbased sensors. Using projections of geosynchronous deployment characteristics and disposal rates, NASA and Kyushu University models of the geosynchronous and super-geosynchronous orbital regimes have examined the sensitivity of the long-term satellite population to various scenarios. Emphasis has been placed on the rate of collisions in the geosynchronous orbit and in the higher disposal orbits and on the significance of cross-regime contamination. The sensitivity of the long-term environment on low velocity (0-1 km/s) collision breakup model parameters and on the minimum height of disposal orbits has also been explored. Results are presented in terms of both satellite population and spatial density.

  8. Radial growth of Tamarix ramosissima responds to changes in the water regime in an extremely arid region of northwestern China

    NASA Astrophysics Data System (ADS)

    Xiao, Shengchun; Xiao, Honglang

    2007-11-01

    The response of radial growth of tamarisk ( Tamarix ramosissima) growing on the shore of West-Juyan Lake, on the Heihe River in northwestern China, to changes in the lake’s water regime was studied using tree-ring chronologies, principal components (PC) analysis, and classical correlation analysis. The first PC accounted for 53.3% of the total variance and reflected a common growth response at different sites. Correlation analysis indicated that fluctuations in the lake’s water level during the growing season (May August) was primarily responsible for variations in the radial growth of tamarisk and explained more of the variance at low-lying sites than at higher sites. The second PC accounted for 30.7% of the total variance and revealed distinct differences in growth response between low-lying sites and those on higher ground. Total annual precipitation played an important role in radial growth of tamarisk at the higher sites. The spatial pattern in the tree-ring chronologies for different sites was performed in the temporal pattern of the tree-ring chronology at the same site. Other factors such as microtopography, soil salinity, sand activity, and browsing by herbivores also affected the radial growth of tamarisk. The diversity in responses to the maximum water table depth for tamarisk in the study area appears to have been caused by local variations in precipitation, which can compensate to some degree for the inability of a plant’s roots to reach the water table.

  9. Characterizing Sub-Daily Flow Regimes: Implications of Hydrologic Resolution on Ecohydrology Studies

    DOE PAGESBeta

    Bevelhimer, Mark S.; McManamay, Ryan A.; O'Connor, B.

    2014-05-26

    Natural variability in flow is a primary factor controlling geomorphic and ecological processes in riverine ecosystems. Within the hydropower industry, there is growing pressure from environmental groups and natural resource managers to change reservoir releases from daily peaking to run-of-river operations on the basis of the assumption that downstream biological communities will improve under a more natural flow regime. In this paper, we discuss the importance of assessing sub-daily flows for understanding the physical and ecological dynamics within river systems. We present a variety of metrics for characterizing sub-daily flow variation and use these metrics to evaluate general trends amongmore » streams affected by peaking hydroelectric projects, run-of-river projects and streams that are largely unaffected by flow altering activities. Univariate and multivariate techniques were used to assess similarity among different stream types on the basis of these sub-daily metrics. For comparison, similar analyses were performed using analogous metrics calculated with mean daily flow values. Our results confirm that sub-daily flow metrics reveal variation among and within streams that are not captured by daily flow statistics. Using sub-daily flow statistics, we were able to quantify the degree of difference between unaltered and peaking streams and the amount of similarity between unaltered and run-of-river streams. The sub-daily statistics were largely uncorrelated with daily statistics of similar scope. Furthermore, on short temporal scales, sub-daily statistics reveal the relatively constant nature of unaltered streamreaches and the highly variable nature of hydropower-affected streams, whereas daily statistics show just the opposite over longer temporal scales.« less

  10. Characterizing Sub-Daily Flow Regimes: Implications of Hydrologic Resolution on Ecohydrology Studies

    SciTech Connect

    Bevelhimer, Mark S.; McManamay, Ryan A.; O'Connor, B.

    2014-05-26

    Natural variability in flow is a primary factor controlling geomorphic and ecological processes in riverine ecosystems. Within the hydropower industry, there is growing pressure from environmental groups and natural resource managers to change reservoir releases from daily peaking to run-of-river operations on the basis of the assumption that downstream biological communities will improve under a more natural flow regime. In this paper, we discuss the importance of assessing sub-daily flows for understanding the physical and ecological dynamics within river systems. We present a variety of metrics for characterizing sub-daily flow variation and use these metrics to evaluate general trends among streams affected by peaking hydroelectric projects, run-of-river projects and streams that are largely unaffected by flow altering activities. Univariate and multivariate techniques were used to assess similarity among different stream types on the basis of these sub-daily metrics. For comparison, similar analyses were performed using analogous metrics calculated with mean daily flow values. Our results confirm that sub-daily flow metrics reveal variation among and within streams that are not captured by daily flow statistics. Using sub-daily flow statistics, we were able to quantify the degree of difference between unaltered and peaking streams and the amount of similarity between unaltered and run-of-river streams. The sub-daily statistics were largely uncorrelated with daily statistics of similar scope. Furthermore, on short temporal scales, sub-daily statistics reveal the relatively constant nature of unaltered streamreaches and the highly variable nature of hydropower-affected streams, whereas daily statistics show just the opposite over longer temporal scales.

  11. Characterization of density fluctuations during the search for an I-mode regime on the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Marinoni, A.; Rost, J. C.; Porkolab, M.; Hubbard, A. E.; Osborne, T. H.; White, A. E.; Whyte, D. G.; Rhodes, T. L.; Davis, E. M.; Ernst, D. R.; Burrell, K. H.

    2015-09-01

    The I-mode regime, routinely observed on the Alcator C-Mod tokamak, is characterized by an edge energy transport barrier without an accompanying particle barrier and with broadband instabilities, known as weakly coherent modes (WCM), believed to regulate particle transport at the edge. Recent experiments on the DIII-D tokamak exhibit I-mode characteristics in various physical quantities. These DIII-D plasmas evolve over long periods, lasting several energy confinement times, during which the edge electron temperature slowly evolves towards an H-mode-like profile, while maintaining a typical L-mode edge density profile. During these periods, referred to as I-mode phases, the radial electric field at the edge also gradually reaches values typically observed in H-mode. Density fluctuations measured with the phase contrast imaging diagnostic during I-mode phases exhibit three features typically observed in H-mode on DIII-D, although they develop progressively with time and without a sharp transition: the intensity of the fluctuations is reduced; the frequency spectrum is broadened and becomes non-monotonic; two dimensional space-time spectra appear to approach those in H-mode, showing phase velocities of density fluctuations at the edge increasing to about 10 km s-1. However, in DIII-D there is no clear evidence of the WCM. Preliminary linear gyro-kinetic simulations are performed in the pedestal region with the GS2 code and its recently upgraded model collision operator that conserves particles, energy and momentum. The increased bootstrap current and flow shear generated by the temperature pedestal are shown to decrease growth rates, thus possibly generating a feedback mechanism that progressively stabilizes fluctuations.

  12. Rayleigh-Taylor growth measurements of three-dimensional modulations in a nonlinear regime

    SciTech Connect

    Smalyuk, V.A.; Sadot, O.; Betti, R.; Goncharov, V.N.; Delettrez, J.A.; Meyerhofer, D.D.; Regan, S.P.; Sangster, T.C.; Shvarts, D.

    2006-05-15

    An understanding of the nonlinear evolution of Rayleigh-Taylor (RT) instability is essential in inertial confinement fusion and astrophysics. The nonlinear RT growth of three-dimensional (3-D) broadband nonuniformities was measured near saturation levels using x-ray radiography in planar foils accelerated by laser light. The initial 3-D target modulations were seeded by laser nonuniformities and subsequently amplified by the RT instability. The measured modulation Fourier spectra and nonlinear growth velocities are in excellent agreement with those predicted by Haan's model [S. Haan, Phys. Rev. A 39, 5812 (1989)]. These spectra and growth velocities are insensitive to initial conditions. In a real-space analysis, the bubble merger was quantified by a self-similar evolution of bubble size distributions, in agreement with the Alon-Oron-Shvarts theoretical predictions [D. Oron et al. Phys. Plasmas 8, 2883 (2001)].

  13. Characterizing Longitude-Dependent Orbital Debris Congestion in the Geosynchronous Orbit Regime

    NASA Astrophysics Data System (ADS)

    Anderson, Paul V.

    The geosynchronous orbit (GEO) is a unique commodity of the satellite industry that is becoming increasingly contaminated with orbital debris, but is heavily populated with high-value assets from the civil, commercial, and defense sectors. The GEO arena is home to hundreds of communications, data transmission, and intelligence satellites collectively insured for an estimated 18.3 billion USD. As the lack of natural cleansing mechanisms at the GEO altitude renders the lifetimes of GEO debris essentially infinite, conjunction and risk assessment must be performed to safeguard operational assets from debris collisions. In this thesis, longitude-dependent debris congestion is characterized by predicting the number of near-miss events per day for every longitude slot at GEO, using custom debris propagation tools and a torus intersection metric. Near-miss events with the present-day debris population are assigned risk levels based on GEO-relative position and speed, and this risk information is used to prioritize the population for debris removal target selection. Long-term projections of debris growth under nominal launch traffic, mitigation practices, and fragmentation events are also discussed, and latitudinal synchronization of the GEO debris population is explained via node variations arising from luni-solar gravity. In addition to characterizing localized debris congestion in the GEO ring, this thesis further investigates the conjunction risk to operational satellites or debris removal systems applying low-thrust propulsion to raise orbit altitude at end-of-life to a super-synchronous disposal orbit. Conjunction risks as a function of thrust level, miss distance, longitude, and semi-major axis are evaluated, and a guidance method for evading conjuncting debris with continuous thrust by means of a thrust heading change via single-shooting is developed.

  14. Experimental characterization of porosity structure and transport properties changes in limestone undergoing different dissolution regimes

    NASA Astrophysics Data System (ADS)

    Gouze, P.; Luquot, L.; Rodriguez, O.; Mangane, P. O.

    2013-12-01

    Limestone rock dissolution induces geometrical parameters changes such as porosity, pore size distribution (connectivity), or tortuosity which may consequently modify transport properties (permeability, diffusion coefficient). Characterizing these changes is essential for modeling flow and CO2 transport during and after the CO2 injection. Indeed, these changes can affect the storage capacity and the injectivity of the formation. We report experimental results from CO2 rich-brine injection into limestone core samples of 9 mm diameter, 18 mm length. Experiments were performed at in situ conditions (T = 100°C and P = 12 MPa) and with four different CO2 partial pressures (PCO2) varying from 0.034 to 3.4 MPa. X-ray microtomography (XMT) images are used to characterize, from pore scale to Darcy scale, the changes in the structural properties induced by the percolation of the CO2-rich brine. Coupling imaging techniques with sample scale measurements of the time-resolved permeability and chemical fluxes, allows determining the change in the chemical and physical parameters of the sample induced by the dissolution processes. The experiment results show localized dissolution features (wormhole formation) for the highest PCO2, whereas homogeneous dissolution is observed for the lower. The higher the CO2 concentration is the more ramifications at macro scale have growth into the sample and consequently the higher the permeability has increased. During low CO2 concentration injections, the dissolution processes may include transport of fine particles, which locally clog the porous space. This process is controlled by the differential dissolution rate of the calcite cement and calcite grains. This mechanism induces a decrease of permeability (while porosity increases) that may alter the CO2 injectivity.

  15. Characterization of magnetic reconnection in the high-energy-density regime

    NASA Astrophysics Data System (ADS)

    Xu, Z.; Qiao, B.; Chang, H. X.; Yao, W. P.; Wu, S. Z.; Yan, X. Q.; Zhou, C. T.; Wang, X. G.; He, X. T.

    2016-03-01

    The dynamics of magnetic reconnection (MR) in the high-energy-density (HED) regime, where the plasma inflow is strongly driven and the thermal pressure is larger than the magnetic pressure (β >1 ), is reexamined theoretically and by particle-in-cell simulations. Interactions of two colliding laser-produced plasma bubbles with self-generated poloidal magnetic fields of, respectively, antiparallel and parallel field lines are considered. Through comparison, it is found that the quadrupole magnetic field, bipolar poloidal electric field, plasma heating, and even the out-of-plane electric field can appear in both cases due to the mere plasma bubble collision, which may not be individually recognized as evidences of MR in the HED regime separately. The Lorentz-invariant scalar quantity De≃γej .(E +ve×B ) {γe=[1-(ve/c) 2]-1/2 }in the electron dissipation region is proposed as the key sign of MR occurrence in this regime.

  16. Growth and characterization of string ribbon

    SciTech Connect

    Hanoka, J.I.; Behnin, B.; Michel, J.; Symko, M.; Sopori, B.L.

    1995-08-01

    Evergreen Solar, a new photovoltaics company, makes solar cells and modules based on String Ribbon. String Ribbon is a silicon sheet growth method wherein two high temperature strings are pulled through a shallow melt of silicon and a crystalline silicon sheet then grows between the two strings. The strings serve to stabilize the edges of the growing silicon sheet. The growth process is primarily meniscus controlled and, compared to other silicon ribbon growth methods such as d-web and EFG, relatively insensitive to temperature fluctuations as great as {+-}10{degrees}C. Growth speed is about 2 cm/minute.

  17. Fire regimes and tree growth in low rainfall jarrah forest of south-west Australia.

    PubMed

    Burrows, Neil; Ward, Bruce; Robinson, Alex

    2010-06-01

    Regular fuel reduction burning is an important management strategy for reducing the scale and intensity of wildfires in south-west Australian native forests, but the long term effects of this on tree and stand growth are not well understood. Five fire treatments, including application of frequent and infrequent low intensity burns, and 25 years of fire exclusion, were applied to small (4 ha) experimental plots in a low rainfall mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest to investigate the effects of these treatments on tree stem diameter growth, stand basal area increment and tree mortality. Mean tree stem growth measured over 20 years was lowest in the long unburnt treatment compared with the burn treatments, although surface soil nutrient levels were generally higher in the unburnt treatment, suggesting these sites may be moisture limited. There was no clear pattern of the effects of the burn treatments, including the number of fires and the interval between fires, on tree stem growth, stand basal area increment, crown health or mortality. These factors were strongly influenced by dominance condition, with dominant and co-dominant trees growing most and suppressed trees growing least and experiencing the highest mortality levels. There was no evidence of deteriorating tree or stand health that could be attributed to either regular low intensity burning or to a long period (25 years) of fire exclusion. PMID:20405126

  18. Growth and Characterization of Complex Mineral Surfaces

    SciTech Connect

    P. Meakin; E. Jettestuen; B. Jamtveit; Y. Y. Podladchikov; S. deVilliers; H. E. F. Amundsen

    2006-09-01

    Precipitation of mineral aggregates near the Earth's surface or in subsurface fractures and cavities often produces complex microstructures and surface morphologies. Here we demonstrate how a simple surface normal growth (SNG) process may produce microstructures and surface morphologies very similar to those observed in some natural carbonate systems. A simple SNG model was used to fit observed surfaces, thus providing information about the growth history and also about the frequency and spatial distribution of nucleation events during growth. The SNG model can be extended to systems in which the symmetry of precipitation is broken, for example by fluid flow. We show how a simple modification of the SNG model in which the local growth rate depends on the distance from a fluid source and the local slope or fluid flow rate, produces growth structures with many similarities to natural travertine deposits.

  19. [Effects of soil water regimes on the growth of Quercus mongolica seedlings in Changbai Mountains].

    PubMed

    Wang, Miao; Li, Qiurong; Hao, Zhanqing; Dong, Baili

    2004-10-01

    This paper studied the response of the seedlings of Quercus mongolica, one of the dominant tree species in Changbai Mountains, to the artificially controlled three soil water gradients, including their morphology, biomass and photosynthetic characteristics. The results indicated that various water regimes significantly affected the biomass and its distribution pattern in the leaves, branches and roots, as well as the leaf gas exchange. Under soil water stress, the crown structure changed, and the tree height, groundline diameter, single leaf area, and aboveground and belowground biomass were inhibited. As soil water content decreased, the ratio of belowground and aboveground biomass dry weight significantly increased. Water stress had a negative effect on net photosynthetic rate, CO2 use efficiency and carbon use efficiency. The responses of stomatal conductance, transpiration rate and water use efficiency to water stress were complicated. Only at low soil water content, the stomatal conductance and transpiration rate significantly decreased, while water use efficiency increased. It was demonstrated that Quercus mongolica was the tree species with variable resistance to drought, and the resistance could be improved by long-term soil water stress. PMID:15624805

  20. Development of a biocidal treatment regime to inhibit biological growths on cultural heritage: BIODAM

    NASA Astrophysics Data System (ADS)

    Young, M. E.; Alakomi, H.-L.; Fortune, I.; Gorbushina, A. A.; Krumbein, W. E.; Maxwell, I.; McCullagh, C.; Robertson, P.; Saarela, M.; Valero, J.; Vendrell, M.

    2008-12-01

    Existing chemical treatments to prevent biological damage to monuments often involve considerable amounts of potentially dangerous and even poisonous biocides. The scientific approach described in this paper aims at a drastic reduction in the concentration of biocide applications by a polyphasic approach of biocides combined with cell permeabilisers, polysaccharide and pigment inhibitors and a photodynamic treatment. A variety of potential agents were screened to determine the most effective combination. Promising compounds were tested under laboratory conditions with cultures of rock deteriorating bacteria, algae, cyanobacteria and fungi. A subsequent field trial involved two sandstone types with natural biofilms. These were treated with multiple combinations of chemicals and exposed to three different climatic conditions. Although treatments proved successful in the laboratory, field trials were inconclusive and further testing will be required to determine the most effective treatment regime. While the most effective combination of chemicals and their application methodology is still being optimised, results to date indicate that this is a promising and effective treatment for the control of a wide variety of potentially damaging organisms colonising stone substrates.

  1. Effect of nitrogen regime on microalgal lipid production during mixotrophic growth with glycerol.

    PubMed

    Paranjape, Kiran; Leite, Gustavo B; Hallenbeck, Patrick C

    2016-08-01

    Mixotrophic growth of microalgae to boost lipid production is currently under active investigation. Such a process could be of practical importance if a cheap source of organic carbon, such as waste glycerol from biodiesel production, could be used. Several previous studies have already demonstrated that this carbon source can be used by different indigenous strains of microalgae. In this study it is shown that different nitrogen limitation strategies can be applied to further increase lipid production during growth with glycerol. In one strategy, cultures were grown in nitrogen replete medium and then resuspended in nitrogen free medium. In a second strategy, cultures were grown with different initial concentrations of nitrate. Lipid production by the two microalgal strains used, Chlorella sorokiniana (PCH02) and Chlorella vulgaris (PCH05), was shown to be boosted by strategies of nitrogen limitation, but they responded differently to how nitrogen limitation was imposed. PMID:27220067

  2. Growth and nutrition of baldcypress families planted under varying salinity regimes in Louisiana, USA

    USGS Publications Warehouse

    Krauss, K.W.; Chambers, J.L.; Allen, J.A.; Soileau, D.M., Jr.; DeBosier, A.S.

    2000-01-01

    Saltwater intrusion from the Gulf of Mexico is one important factor in the destruction of baldcypress (Taxodium distichum (L.) Rich.) swamps along the Louisiana Gulf Coast, USA. Recent restoration efforts have focused on identification of baldcypress genotypes with greater tolerance to saline conditions than previously reported. To date, salt tolerance investigations have not been conducted under saline field conditions. In 1996, therefore, three plantations were established with 10 half-sib genotype collections of baldcypress in mesohaline wetlands. Tree survival and growth were measured at the end of two growing seasons, and foliar ion concentrations of Na, Cl, K, and Ca and available soil nutrients were measured during the 1996 growing season. In general, soil nutrient concentrations exceeded averages found in other baldcypress stands in the southeastern United States. Seedlings differed among sites in all parameters measured, with height, diameter, foliar biomass, and survival decreasing as site salinity increased. Average seedling height at the end of two years, for example, was 196.4 cm on the lowest salinity site and 121.6 cm on the highest. Several half-sib families maintained greater height growth increments (ranging from 25.5 to 54.5 cm on the highest salinity site), as well as lower foliar ion concentrations of K, Cl, and Ca. Results indicate that genotypic screening of baldcypress may improve growth and vigor of seedlings planted within wetlands impacted by saltwater intrusion.

  3. Harmonic growth of spherical Rayleigh-Taylor instability in weakly nonlinear regime

    SciTech Connect

    Liu, Wanhai; Chen, Yulian; Yu, Changping E-mail: lixl@imech.ac.cn; Li, Xinliang E-mail: lixl@imech.ac.cn

    2015-11-15

    Harmonic growth in classical Rayleigh-Taylor instability (RTI) on a spherical interface is analytically investigated using the method of the parameter expansion up to the third order. Our results show that the amplitudes of the first four harmonics will recover those in planar RTI as the interface radius tends to infinity compared against the initial perturbation wavelength. The initial radius dramatically influences the harmonic development. The appearance of the second-order feedback to the initial unperturbed interface (i.e., the zeroth harmonic) makes the interface move towards the spherical center. For these four harmonics, the smaller the initial radius is, the faster they grow.

  4. Experimental observation of Rayleigh-Taylor growth as a function of wavelength in the warm dense matter regime

    NASA Astrophysics Data System (ADS)

    Huntington, C. M.; Arsenlis, A.; Maddox, B. R.; Park, H.-S.; Prisbrey, S. T.; Weber, S. V.; Wehrenberg, C. E.; Remington, B. A.

    2014-10-01

    ``Classical'' Rayleigh-Taylor (RT) growth is characterized by a growth rate γ =√{ kgAn } , where k is the wavelength of the unstable mode, g is the acceleration, and the Atwood An number characterizes the magnitude of the density jump at the interface. Here we present the results of a set of experiments using face-on x-ray radiography to measure RT growth in a plastic rippled sample. Acceleration of the sample is provided by the stagnation of a releasing shocked plastic ``reservoir,'' which is directly driven by approximately 1 kJ of laser energy at the OMEGA facility. The growth of pre-imposed ripples is recorded using transmission x-ray radiography of a vanadium Heα source, where the opacity of the sample is calibrated to the ripple amplitude. We report the results of experiments at 30 μm and 60 μm initial wavelengths, and compare the data to 2D hydrodynamic simulations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  5. Adapting of the Background-Oriented Schlieren (BOS) Technique in the Characterization of the Flow Regimes in Thermal Spraying Processes

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Abdulgader, M.; Rademacher, H. G.; Anjami, N.; Hagen, L.

    2014-01-01

    In thermal spraying technique, the changes in the in-flight particle velocities are considered to be only a function of the drag forces caused by the dominating flow regimes in the spray jet. Therefore, the correct understanding of the aerodynamic phenomena occurred at nozzle out let and at the substrate interface is an important task in the targeted improvement in the nozzle and air-cap design as well as in the spraying process in total. The presented work deals with the adapting of an innovative technique for the flow characterization called background-oriented Schlieren. The flow regimes in twin wire arc spraying (TWAS) and high velocity oxygen fuel (HVOF) were analyzed with this technique. The interfering of the atomization gas flow with the intersected wires causes in case of TWAS process a deformation of the jet shape. It leads also to areas with different aero dynamic forces. The configurations of the outlet air-caps in TWAS effect predominantly the outlet flow characteristics. The ratio between fuel and oxygen determine the dominating flow regimes in the HVOF spraying jet. Enhanced understanding of the aerodynamics at outlet and at the substrate interface could lead to a targeted improvement in thermal spraying processes.

  6. Contribution of silver nanoparticles to extend Salmonella typhimurium growth under various respiration regimes.

    PubMed

    Hidouri, Slah; Yohmes, Mannoubia Ben; Landoulsi, Ahmed

    2016-10-01

    Living cells interact with different forms of metal; the resulted biochemical alteration depends on the dose. Over an average dose in ionic form, metals interact with respiration processes at various levels, and it induces oxidative stress by shifting the whole oxydoreduction equilibrium. To correct the toxicity, cell develops different ways to cancel the effect of the exceeded charges, and it reduces the ion to get a more stable form. In the case of nanoparticles, the reactivity of surface has been enhanced that can alter the biological mechanisms; the cell may develop different strategies to minimize this reactivity. The current study is focused on the pursuing of cell behavior regarding the presence of nanoparticles and their associated metals. Nanoparticles have been synthesized using bio-reducing agents and then were structurally characterized using X-ray diffraction, UV-Vis, and infra-red spectroscopy. The oxydoreduction flexibility of the post-synthesis modified nanoparticles was tested in vitro. Interactions with cells were done using Salmonella under various respiration conditions. The final results show the possible correction of oxidative stress effects and the recuperation of respiration. PMID:27287758

  7. Effects of flooding regime and seedling treatment on early survival and growth of nuttall oak

    USGS Publications Warehouse

    Burkett, V.R.; Draugelis-Dale, R.O.; Williams, H.M.; Schoenholtz, S.H.

    2005-01-01

    Effects of flooding on survival and growth of three different types of Nuttall oak (Quercus texana Buckl.) seedlings were observed at the end of third and fifth growing seasons at Yazoo National Wildlife Refuge, Mississippi, U.S.A. Three types of seedlings were planted in January 1995 in a split-plot design, with four replications at each of two elevations on floodprone, former cropland in Sharkey clay soil. The lower of the two planting elevations was inundated for 21 days during the first growing season, whereas the higher elevation did not flood during the 5-year period of this study. The three types of 1-0 seedlings were bareroot seedlings, seedlings grown in containers (3.8 ?? 21a??cm plastic seedling cones), and container-grown seedlings inoculated with vegetative mycelia of Pisolithus tinctorius (Pers.) Coker. Survival of all the three seedling types was greatest at the lower, intermittently flooded elevation, indicating that drought and related effects on plant competition were more limiting to seedling survival than flooding. At the lower elevation, survival of mycorrhizal-inoculated container seedlings was greater than that of noninoculated container seedlings. Survival among bareroot seedlings and inoculated container seedlings was not significantly different at either elevation. At the higher, nonflooded elevation, however, bareroot seedling survival was greater than the survival of container seedlings without inoculation. Differences were significant among the inoculated and the noninoculated container seedlings, with higher survival of inoculated seedlings at both elevations, though differences were only significant in year 3. At the end of the fifth year, height of bareroot seedlings was significantly greater than the heights of both types of container-grown seedlings at both planting elevations. Because seedlings grown in the plastic seedlings cones did not survive better than the bareroot seedlings at either planting elevation, the bareroot stock

  8. Characterization of forest vegetation-climate feedback regimes by satellite remote sensing imagery

    NASA Astrophysics Data System (ADS)

    Zoran, Maria

    Vegetation and climate interact through a series of complex feedbacks, which are not very well understood.The patterns of forest vegetation are largely determined by temperature, precipitation, solar irradiance, soil conditions and CO2 concentration. Vegetation impacts climate directly through moisture, energy, and momentum exchanges with the atmosphere and indirectly through biogeochemical processes that alter atmospheric CO2 concentration. Changes in forest vegetation landuse-landcover alter the surface albedo and radiation fluxes, leading to a local temperature change and eventually a vegetation response. This albedo (energy) feedback is particularly important when forests mask snow cover. Forest vegetation-climate feedback regimes are designated based on the temporal correlations between the vegetation and and the surface temperature and precipitation. The different feedback regimes are linked to the relative importance of vegetation and soil moisture in determining land-atmosphere interactions. The spatio-temporal dynamics are assessed in terms of the NDVI-surface temperature correlations.Observed vegetation feedbacks on temperature and precipitation are assessed based on Landsat TM, ETM, MODIS and IKONOS satellite data across the forested areas in North/Eastern part of Bucharest town, Romania for a period of 1984 -2007 period. The computed feedback parameters can be used to evaluate vegetation-climate interactions simulated by models with dynamic vegetation. Specific aim of this paper is to assess the forest vegetationclimate feedbacks on forest ecosystem and its biodiversity as well as on adjacent environment areas and to provide early warning strategies on the remote sensing spectral information basis.

  9. Characterizing dichotomous fire regimes of southern California: climate, vegetation and topography

    NASA Astrophysics Data System (ADS)

    Kolden, C.; Abatzoglou, J. T.

    2013-12-01

    Southern California Mediterranean ecosystems have long been a subject of wildfire research, in part because of the extensive Wildland Urban Interface in the region. This mix of homes and vegetation at the edge of wildlands has resulted in several of the costliest wildfire events in US history due to the number of homes burned, and its extent is projected to increase significantly over the next 50 years. As such, there has been considerable investment is identifying fire regime characteristics and potential mitigation measures in the region. However, all previous wildfire research in the region has initiated from the assumption that the dominant fire regime is associated with autumn katabatic winds, known locally as Santa Ana winds or Sundowners. To-date, there has been no effort to determine whether this is an accurate assumption, or whether the fire regime is more complex. Here, we utilize a dataset of large wildfires (>40ha) from 1948-2010 and a chronology of Santa Ana (SA) wind occurrence to disaggregate two distinct fire regimes in southwestern California: wildfires associated with SA wind occurrence events, and those not associated with Santa Ana conditions (NSA) that are fuel- and topography-driven instead. By decomposing burned area into SA and NSA fires, significant differences in seasonal, biogeographic and topographic characteristics were found, as well as distinct and significantly stronger climate-fire relationships than previously reported. NSA area burned was associated with summer fires, peaking in July, and significantly higher elevation, greater forested area, steeper slopes, and broadly across all aspects. SA area burned was associated with autumn fires, peaking in October, and significantly lower elevation, greater shrubland area, lower slopes, and more southeastern aspects. Annual burned area in NSA fires was associated with low spring precipitation, high vapor pressure deficit and low fuel moistures during the summer months that increase the

  10. Growth and characterization of GE nanocrystals

    SciTech Connect

    Guha, S., Naval Research Laboratory

    1998-05-01

    We have synthesized Ge nanocrystals of sizes 4, 8, and 12 nm by ion-implanting Ge+ ions into thermally grown Si0{sub 2} films and subsequent annealing of the films at 8300 C for 30 min in nitrogen. These films were characterized by x-ray, transmission electron microscopy (TEM), and Raman spectroscopy. A distribution of particle size was identified by TEM in a 1 00 nm band below the surface. Particle sizes were estimated by these 3 techniques.

  11. Growth and characterization of sidewall graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Baringhaus, J.; Aprojanz, J.; Wiegand, J.; Laube, D.; Halbauer, M.; Hübner, J.; Oestreich, M.; Tegenkamp, C.

    2015-01-01

    We study the growth of epitaxial graphene nanoribbons on silicon carbide mesa sidewalls by means of scanning probe techniques, local transport, and Raman spectroscopy. The sidewall nanoribbons are demonstrated to consist of charge neutral monolayer graphene with a zig-zag type orientation. Two types of roughness, the step density of the substrate and the roughness of the sidewalls, were identified as being detrimental to the transport properties of these ribbons. By means of 4-point probe experiments, single channel ballistic transport was observed with a mean free path limited by the width of the underlying substrate terraces. Moreover, a transition from ballistic to one-dimensional diffusive transport can be obviously triggered by an increased roughness of the sidewall, e.g., by an enlarged depth of the mesa.

  12. Cell growth characterization using multi-electrode bioimpedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Yi-Yu; Huang, Ji-Jer; Huang, Yu-Jie; Cheng, Kuo-Sheng

    2013-03-01

    Cell growth characterization during culturing is an important issue in a variety of biomedical applications. In this study an electrical bioimpedance spectroscopy-based multi-electrode culture monitoring system was developed to characterize cell growth. A PC12 cell line was cultured for the cell growth study. The bioimpedance variations for PC12 cell growth within the initial 12 h were measured over a range between 1 kHz and 4 MHz at three different medium concentrations. Within this frequency range, the largest bioimpedance value was 1.9 times the smallest bioimpedance value. The phase angle decreased over the range from 1 to 10 kHz when cells were growing. Then, the phase angle approached a constant over the frequency range between 10 kHz and 2 MHz. Thereafter, the phase angle increased rapidly from 20 to 52 degrees during cell culturing between 8 and 12 h at 4 MHz. The maximum cell number after culturing for 12 h increased by 25.8% for the control sites with poly-D-lysine (PDL) pastes. For the normal growth factor, the cell number increased up to 4.78 times from 8 to 12 h, but only 0.96 and 1.60 times for the other two medium growth factors. The correlation coefficients between impedance and cell number were 0.868 (coating with PDL), and 0.836 (without PDL) for the normal concentration medium. Thus, impedance may be used as an index for cell growth characterization.

  13. The role of density dependence in growth patterns of ceded territory walleye populations of northern Wisconsin: Effects of changing management regimes

    USGS Publications Warehouse

    Sass, G.G.; Hewett, S.W.; Beard, T.D., Jr.; Fayram, A.H.; Kitchell, J.F.

    2004-01-01

    We assessed density-related changes in growth of walleye Sander vitreus in the ceded territory of northern Wisconsin from 1977 to 1999. We used asymptotic length (Lz), growth rate near t0 (??), and body condition as measures of walleye growth to determine the relationship between growth and density. Among lakes, there was weak evidence of density-dependent growth: adult density explained only 0-6% of the variability in the growth metrics. Within lakes, growth was density dependent. Lz, ??, and body condition of walleyes changing with density for 69, 28, and 62% of the populations examined, respectively. Our results suggest that walleye growth was density dependent within individual lakes. However, growth was not coherently density dependent among lakes, which was possibly due to inherent differences in the productivity, surface area, forage base, landscape position, species composition, and management regime of lakes in the ceded territory. Densities of adult walleyes averaged 8.3 fish/ha and did not change significantly during 1990-1999. Mean Lz and body condition of walleyes were signilicantly higher before 1990 than after 1990, which may indicate an increase in density due to changes in management regimes. The observed growth changes do not appear to be a consequence of the statewide 15-in minimum size limit adopted in 1990 but rather a response to the treaty rights management regime. We conclude that walleye growth has the potential to predict regional-scale adult walleye densities if lake-specific variables are included in a model to account for regional-scale differences among walleye populations and lakes.

  14. Mycorrhizal symbiosis effects on growth of chalk false-brome (Brachypodium pinnatum) are dependent on the environmental light regime.

    PubMed

    Füzy, Anna; Bothe, Hermann; Molnár, Edit; Biró, Borbála

    2014-03-01

    AMF (arbuscular mycorrhizal fungi) colonization of the grass chalk false-brome (Brachypodium pinnatum (L.) P. B.) was studied in selected habitats under spatially different light regimes: (a) shade condition under oak trees, (b) half shade in a shrubby area and (c) full-sun conditions on unshaded grassland. This study assessed the variations in AMF colonization of the grass dependent on the light supply in field habitats. Soil, root and shoot samples were collected four times during the vegetation period (in June, July, September and October). Root colonization, root and shoot biomass as well as soil water content were determined. The highest rate of AMF colonization was detected in June under half-sun and full-sun conditions, where about 50% of the roots were colonized. The average amount of arbuscules was less than 20% in the roots at the three sites, with the highest number of arbuscules in June, under half-sun and full-sun conditions, however, not under the trees. Overall, best mycorrhizal colonization occurred during summer, and its rate decreased in autumn. This tendency inversely correlated with the amount of precipitation, and thus with the water content of soils. The high colonization rate of the examined root samples, and also its seasonal fluctuation, might reflect the importance of the symbiosis where inorganic nutrients and water are the growth-limiting factors. The marginal AMF colonization of chalk false-brome under shade conditions indicates that plants do not use AMF under all stress conditions. When low light limits photosynthesis and thus growth of the plants, they dispense with the colonization of AMF in order to save the expenditure of organic carbon. PMID:24484951

  15. Growth and palmitoleic acid accumulation of filamentous oleaginous microalgae Tribonema minus at varying temperatures and light regimes.

    PubMed

    Wang, Hui; Gao, Lili; Zhou, Wenjun; Liu, Tianzhong

    2016-10-01

    Palmitoleic acid (C16:1Δ9), contributes greatly to human health, industrial chemicals and biodiesel. The filamentous oleaginous microalgae Tribonema sp. has been identified as a highly efficient producer of palmitoleic acid. Temperature and light regime were adapted to regulate the palmitoleic acid content in this study. Strain T. minus was able to grow well at all the tested temperatures, even at 5 °C. The optimum temperature for palmitoleic acid accumulation (54.25 % of total fatty acid) was 25 °C. Moreover, both light intensity and photoperiod affect the growth, lipid content and fatty acid files of T. minus. The culture exposed to 240 μmol photons m(-2) s(-1) with a photoperiod of 24:0 showed the highest biomass (6.87 g L(-1)) and biggest lipid content (61.27 % of dry weight), whereas the most amount of palmitoleic acid (50.47 % of total fatty acid) was detected at 120 μmol photons m(-2) s(-1). These findings make tangible contributions to culture T. minus for commercial production of lipid or palmitoleic acid. PMID:27250652

  16. Effect of different arbuscular mycorrhizal fungi on growth and physiology of maize at ambient and low temperature regimes.

    PubMed

    Chen, Xiaoying; Song, Fengbin; Liu, Fulai; Tian, Chunjie; Liu, Shengqun; Xu, Hongwen; Zhu, Xiancan

    2014-01-01

    The effect of four different arbuscular mycorrhizal fungi (AMF) on the growth and lipid peroxidation, soluble sugar, proline contents, and antioxidant enzymes activities of Zea mays L. was studied in pot culture subjected to two temperature regimes. Maize plants were grown in pots filled with a mixture of sandy and black soil for 5 weeks, and then half of the plants were exposed to low temperature for 1 week while the rest of the plants were grown under ambient temperature and severed as control. Different AMF resulted in different root colonization and low temperature significantly decreased AM colonization. Low temperature remarkably decreased plant height and total dry weight but increased root dry weight and root-shoot ratio. The AM plants had higher proline content compared with the non-AM plants. The maize plants inoculated with Glomus etunicatum and G. intraradices had higher malondialdehyde and soluble sugar contents under low temperature condition. The activities of catalase (CAT) and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology and AM symbiosis can improve maize seedlings tolerance to low temperature stress. PMID:24895680

  17. Characterization and comparison of microstructures in the shaped-charge regime: Copper and tantalum

    SciTech Connect

    Gurevitch, A.C.; Murr, L.E.; Shih, H.K.; Niou, C.S.; Advani, A.H.; Manuel, D. ); Zernow, L. )

    1993-04-01

    Light microscopy, scanning electron microscopy, and transmission electron microscopy techniques were employed, along with a novel technique for building up small, recovered jet fragments using electrodeposition of copper, to examine specific segments of fabricated shaped charge liner cones and corresponding, residual jet fragments. Oxygen-free electronic copper and tantalum shaped charge regimes (liner cones and recovered jet fragments) were compared, and a reduction in the average grain size of recovered jet fragments as compared to the starting liner cones was a consistent observation. The average grain sizes for all cones was 35 [mu]m, and the maximum grain reduction occurred for an annealed, equiaxed tantalum cone, which resulted in a residual jet fragment grain size between 1 and 5 [mu]m. This is indicative of dynamic recrystallization during jet elongation and microstructure evolution. The most recent US military use of shaped charges was in the high explosive antitank shells used in the 1990-1991 conflict with Iraq. Shaped charges are also used in the oil and gas industries, steel industries, mining and quarrying, specialty cutting, and perhaps most prominently in building demolition work within cities.

  18. Growth and characterization of (110) InAs quantum well metamorphic heterostructures

    SciTech Connect

    Podpirka, Adrian A. Katz, Michael B.; Twigg, Mark E.; Mack, Shawn; Bennett, Brian R.; Shabani, Javad; Palmstrøm, Chris J.

    2015-06-28

    An understanding of the growth of (110) quantum wells (QWs) is of great importance to spin systems due to the observed long spin relaxation times. In this article, we report on the metamorphic growth and characterization of high mobility undoped InAs (110) QWs on GaAs (110) substrates. A low-temperature nucleation layer reduces dislocation density, results in tilting of the subsequent buffer layer and increases the electron mobility of the QW structure. The mobility varies widely and systematically (4000–16 000 cm{sup 2}/Vs at room temperature) with deposition temperature and layer thicknesses. Low-temperature transport measurements exhibit Shubnikov de-Haas oscillations and quantized plateaus in the quantum Hall regime.

  19. Walker Branch Throughfall Displacement Experiment Data Report: Site Characterization, System Performance, Weather, Species Composition, and Growth

    SciTech Connect

    Hanson, P.J.

    2001-09-04

    This numeric data package provides data sets, and accompanying documentation, on site characterization, system performance, weather, species composition, and growth for the Throughfall Displacement Experiment, which was established in the Walker Branch Watershed of East Tennessee to provide data on the responses of forests to altered precipitation regimes. The specific data sets include soil water content and potential, coarse fraction of the soil profile, litter layer temperature, soil temperature, monthly weather, daily weather, hourly weather, species composition of trees and saplings, mature tree and sapling annual growth, and relative leaf area index. Fortran and SAS{trademark} access codes are provided to read the ASCII data files. The data files and this documentation are available without charge on a variety of media and via the Internet from the Carbon Dioxide Information Analysis Center (CDIAC).

  20. A Regional Hydrologic Classification of Unregulated Rivers: Towards the Development of Natural Flow Regime Characterization and Environmental Flows in California

    NASA Astrophysics Data System (ADS)

    Lane, B.; Sandoval Solis, S.

    2014-12-01

    Alterations to flow regimes from regulation and climate change affect the biophysical functioning of rivers. Re-operating reservoirs to provide environmental flows - the quantity, quality, and timing of water to sustain natural river functions and species - is now widely applied in multi-objective water resources management. However, the absence of a quantitative, transferable framework for evaluating the relationships between hydrologic inputs, geomorphic functions, and ecological responses, remains a major limitation to setting environmental flows standards. This research addresses this gap by developing a hydrologic classification framework for the State of California that balances operational practicality with scientific defensibility. The framework organizes river reaches into: (1) natural flow classes based on (a) a classification model that clusters hydrologic indices calculated directly from unimpaired streamflow data, and (b) a regression model using a set of climatic, landscape, and local geomorphic controls over the flow regime, and (2) functional zones constrained by temporal (seasonal) ranges and hydrologic (average flow percentile-based) thresholds (e.g. summer low flows). The framework is then used to (1) identify major climatic, landscape, and local geomorphic controls over prototypical flow regime signatures, and (2) characterize key natural functions and processes expected of reaches of each flow class and functional zone during wet, dry, and normal water year types. Organizing hydrologic data in this manner provides a means of comparison and transferability of ecologically-significant hydrologic and geomorphic information across reaches of all major flow classes seen in California, both regulated and unregulated. Through this framework, transferable relationships between hydrologic and physiographic conditions, flow alteration, and ecological metrics can be developed and tested on the basis of data obtained from a limited set of study sites.

  1. Evaluation of feed and feeding regime on growth performance, flesh quality and fecal viscosity of Atlantic salmon ( Salmo salar L.) in recirculating aquaculture systems

    NASA Astrophysics Data System (ADS)

    Sun, Guoxiang; Liu, Ying; Li, Yong; Li, Xian; Wang, Shunkui

    2015-10-01

    The effects of different feeds and feeding regimes on growth performance, flesh quality and fecal viscosity of Atlantic salmon ( Salmo salar L.) in recirculating aquaculture systems (RAS) were investigated. Fish (initial body weight of 1677 g ± 157 g) were fed with four commercial feeds (Nosan salmon-NS, Aller gold-AG, Skretting salmon-SS and Han ye-HY) in two feeding regimes (80% and 100% satiation) for 78 d. The results showed that salmon specific growth ratio (SGR) and weight gain ratio (WGR) were significantly affected by feed type and feeding regime ( P < 0.05). Feed conversion ratio (FCR) varied between 0.93 and 3.40, which was significantly affected by feed type ( P < 0.05), and slightly improved with increased satiation degree. The activities of digestive enzymes including protease, lipase and amylase were also significantly affected by feed type and feeding regime ( P < 0.05), increasing with satiation degree. Flesh qualities for vitamin E, hydroxyproline (HYP), liquid loss and muscle pH among all groups showed significant differences ( P < 0.05), ranging from 26.67 to 29.67, while no obvious difference was found in flesh color. Fecal viscosity for different treatments showed no significant difference, though improvement was found in 100% satiation group. From present experiment, it was concluded that both feed type and feeding regime can affect the important quality attributes of Atlantic salmon.

  2. Characterization of delamination onset and growth in a composite laminate

    NASA Technical Reports Server (NTRS)

    Obrien, T. K.

    1981-01-01

    The onset and growth of delaminations in unnotched (+ or - 30/+ or - 30/90/90 bar) sub S graphite epoxy laminates is described quantitatively. These laminates, designed to delaminate at the edges under tensile loads, were tested and analyzed. Delamination growth and stiffness loss were monitored nondestructively. Laminate stiffness decreased linearly with delamination size. The strain energy release rate, G, associated with delamination growth, was calculated from two analyses. A critical G for delamination onset was determined, and then was used to predict the onset of delaminations in (+45 sub n/-45 sub n/o sub n/90 sub n) sub s (n=1,2,3) laminates. A delamination resistance curve (R curve) was developed to characterize the observed stable delamination growth under quasi static loading. A power law correlation between G and delamination growth rates in fatigue was established.

  3. Growth and Characterization of Graphene on Single Crystal Cu Substrates

    NASA Astrophysics Data System (ADS)

    Robinson, Z. R.; Tyagi, P.; Geisler, H.; Ventrice, C. A., Jr.; Bol, A. A.; Hannon, J. B.

    2012-02-01

    One of the key issues for the use of CVD graphene in device applications is the influence of defects on the transport properties of the graphene. Therefore, it is important to understand the influence of the substrate on the orientation of the graphene. Growth of graphene films on Cu(111) has the potential for producing films with a low defect density because of the hexagonal symmetry of the substrate and relatively small lattice mismatch, whereas growth on Cu(100) is expected to result in multi-domain growth because of its square symmetry. In this study, graphene films were grown on Cu single crystal substrates, and characterized with LEEM, LEED, SEM, AFM, and Raman spectroscopy. The clean Cu substrates were prepared by sputtering and annealing in UHV. For the initial growth studies, the samples were transferred to a tube furnace for graphene growth using a technique optimized for Cu foils. The UHV system has recently been modified with a button heater compatible with the conditions needed for graphene growth to enable in-situ growth and characterization.

  4. Survival, development, and growth of fall Chinook salmon embryos, alevin, and fry exposed to variable thermal and dissolved oxygen regimes

    SciTech Connect

    Geist, David R.; Abernethy, Cary S.; Hand, Kristine D.; Cullinan, Valerie I.; Chandler, James A.; Groves, Philip

    2006-11-15

    Some fall Chinook salmon (Oncorhynchus tshawytscha) initiate spawning in the Snake River downstream of Hells Canyon Dam at temperatures that exceed 13?C and at intergravel dissolved oxygen concentrations that are less than 8 mg O2/L. Although water temperature declines and dissolved oxygen increases soon after spawning, these temperature and dissolved oxygen levels do not meet the water quality standards established by the states of Oregon and Idaho for salmonid spawning. Our objective was to determine if temperatures from 13 to 17 C and dissolved oxygen levels from 4 to greater than 8 mg O2/L during the first 40 days of incubation followed by declining temperature and rising dissolved oxygen affected survival, development, and growth of Snake River fall Chinook salmon embryos, alevins, and fry. During the first 40 days of incubation, temperatures were adjusted downward approximately 0.2 C/day and oxygen was increased in increments of 2 mg O2/L to mimic the thermal and oxygen regime of the Snake River where these fish spawn. At 40 days post-fertilization, embryos were moved to a common exposure regime that followed the thermal and dissolved oxygen profile of the Snake River through emergence. Mortality of fall Chinook salmon embryos increased markedly at initial incubation temperatures equal to or greater than 17?C, and a rapid decline in survival occurred between 16.5 C and 17 C, with no significant difference in survival at temperatures less than or equal to 16.5 C. Initial dissolved oxygen levels as low as 4 mg O2/L over a range of initial temperatures from 15 to 16.5 C did not affect embryo survival to emergence. There were no significant differences across the range of initial temperature exposures for alevin and fry size at hatch and emergence. The number of days from fertilization to eyed egg, hatch, and emergence was highly related to temperature and dissolved oxygen; it took from 6 to 10 days longer to reach hatch at 4 mg O2/L than at saturation and up to

  5. Physical characterization of Rhipsalis (Cactaceae) fruits and seeds germination in different temperatures and light regimes.

    PubMed

    Lone, A B; Colombo, R C; Andrade, B L G; Takahashi, L S A; Faria, R T

    2016-06-01

    The germination characteristics of the native cactus species are poorly known, being the temperature and the light the factors that the most interferes in that process. Thus, the objective of the present work was to characterize the fruits and evaluate the influence of the temperature and the light in the seed germination of Rhipsalis floccosa, Rhipsalis pilocarpa and Rhipsalis teres. The tested constant temperatures were 15, 20, 25, 30 and 35 °C and the alternate of 20-30 °C and 25-35 °C in a photoperiod of 10 hours, and with determination of the most appropriate temperature, the germination was tested in light absence. The germination percentage, the index of germination speed and medium time of germination were evaluated. For R. floccosa, the highest germination percentage was at 20 °C. For R. pilocarpa and R. teres, the highest germination percentages occurred in 15 °C and 20 °C. There was correlation to germination percentage between the three species, indicating that they had similar germination behavior. Total absence of germination was verified for the three species in condition of light absence. In conclusion, the temperature of 20 °C is the most suitable for the seed germination of R. floccosa. For the species R. pilocarpa and R. teres, the temperatures of 15 and 20 °C are the most suitable. PMID:26934150

  6. Characterization of antirelaxation-coated vapor cells in high-temperature regime

    NASA Astrophysics Data System (ADS)

    Li, Wenhao; Balabas, Mikhail; Pustelny, Szymon; Wickenbrock, Arne; Budker, Dmitry

    2016-05-01

    Antirelaxation-coated vapor cells are widely used in modern atomic physics experiments due to the coating's ability to maintain spin polarization during wall collisions. We characterize the performance of vapor cells with different coating materials by measuring longitudinal spin relaxation and vapor density at temperatures of up to 90° C. The longitudinal spin relaxation time (τrel) is measured with a modified version of ``relaxation in the dark'' technique and the vapor density (n) is obtained by fitting atomic absorption spectrum with linear absorption function. The spin-projection-noise-limited (or atomic shot noise limited) sensitivity for atomic magnetometers is δBSNL 1 /√{ nτrel T } , where T is measurement time. Therefore, by showing the product of the longitudinal spin relaxation time and the vapor density increases with temperature, we demonstrate the potential of antirelaxation-coated cells in applications of future high-sensitivity magnetometers. W.L. would like to acknowledge support from the China Scholarship Council (CSC) enabling his research at the University of California at Berkeley.

  7. Femtosecond Laser Tagging Characterization of a Sweeping Jet Actuator Operating in the Compressible Regime

    NASA Technical Reports Server (NTRS)

    Peters, Christopher J.; Miles, Richard B.; Burns, Ross A.; Bathel, Brett F.; Jones, Gregory S.; Danehy, Paul M.

    2016-01-01

    A sweeping jet (SWJ) actuator operating over a range of nozzle pressure ratios (NPRs) was characterized with femtosecond laser electronic excitation tagging (FLEET), single hot-wire anemometry (HWA) and high-speed/phase-averaged schlieren. FLEET velocimetry was successfully demonstrated in a highly unsteady, oscillatory flow containing subsonic through supersonic velocities. Qualitative comparisons between FLEET and HWA (which measured mass flux since the flow was compressible) showed relatively good agreement in the external flow profiles. The spreading rate was found to vary from 0.5 to 1.2 depending on the pressure ratio. The precision of FLEET velocity measurements in the external flow field was poorer (is approximately equal to 25 m/s) than reported in a previous study due to the use of relatively low laser fluences, impacting the velocity fluctuation measurements. FLEET enabled velocity measurements inside the device and showed that choking likely occurred for NPR = 2.0, and no internal shockwaves were present. Qualitative oxygen concentration measurements using FLEET were explored in an effort to gauge the jet's mixing with the ambient. The jet was shown to mix well within roughly four throat diameters and mix fully within roughly eight throat diameters. Schlieren provided visualization of the internal and external flow fields and showed that the qualitative structure of the internal flow does not vary with pressure ratio and the sweeping mechanism observed for incompressible NPRs also probably holds for compressible NPRs.

  8. Characterization of radiation regimes in nonrandom forest canopies: theory, measurements, and a simplified modeling approach.

    PubMed

    Kucharik, Christopher J.; Norman, John M.; Gower, Stith T.

    1999-09-01

    We used field measurements and Monte Carlo simulations of canopy gap-size distribution and gap fraction to examine how beam radiation interacts with clumped boreal forest canopies of aspen (Populus tremuloides Michx.), black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.). We demonstrate that the Beer-Lambert law can be modified to accommodate transmission of radiation through a clumped forest canopy as a function of path length or sun zenith angle. Multiband Vegetation Imager (MVI) measurements and Monte Carlo simulations showed that values of the zenith element clumping index (Omega(e)(0)) are typically between 0.4 and 0.5 in jack pine and black spruce and 0.65 in aspen. Estimates of LAI obtained from MVI measurements of the canopy gap fraction and adjusted for canopy clumping and branch architecture yielded LAI values of 3.0 in jack pine, 3.3 in aspen, and about 6.0 in black spruce. These LAI estimates were within 10-25% of direct measurements made at the same sites. Data obtained with the MVI, along with numerical simulations, demonstrated that assumptions of random foliage distributions in boreal forests are invalid and could yield erroneous values of LAI measured by indirect techniques and false characterizations of atmosphere-biosphere interactions. Monte Carlo simulations were used to develop a general equation for beam radiation penetration as a function of zenith angle in clumped canopies. The essential measurements included stem spacing, crown diameter, crown depth, and within-crown gap fraction. PMID:12651308

  9. Characterization of Ethiopian mega hydrogeological regimes using GRACE, TRMM and GLDAS datasets

    NASA Astrophysics Data System (ADS)

    Awange, J. L.; Gebremichael, M.; Forootan, E.; Wakbulcho, G.; Anyah, R.; Ferreira, V. G.; Alemayehu, T.

    2014-12-01

    Understanding the spatio-temporal characteristics of water storage changes is crucial for Ethiopia, a country that is facing a range of challenges in water management caused by anthropogenic impacts as well as climate variability. In addition to this, the scarcity of in situ measurements of soil moisture and groundwater, combined with intrinsic "scale limitations" of traditional methods used in hydrological characterization are further limiting the ability to assess water resource distribution in the region. The primary objective of this study is therefore to apply remotely sensed and model data over Ethiopia in order to (i) test the performance of models and remotely sensed data in modeling water resources distribution in un-gauged arid regions of Ethiopia, (ii) analyze the inter-annual and seasonal variability as well as changes in total water storage (TWS) over Ethiopia, (iii) understand the relationship between TWS changes, rainfall, and soil moisture anomalies over the study region, and (iv) identify the relationship between the characteristics of aquifers and TWS changes. The data used in this study includes; monthly gravity field data from the Gravity Recovery And Climate Experiment (GRACE) mission, rainfall data from the Tropical Rainfall Measuring Mission (TRMM), and soil moisture from the Global Land Data Assimilation System (GLDAS) model. Our investigation covers a period of 8 years from 2003 to 2011. The results of the study show that the western part and the north-eastern lowlands of Ethiopia experienced decrease in TWS water between 2003-2011, whereas all the other regions gained water during the study period. The impact of rainfall seasonality was also seen in the TWS changes. Applying the statistical method of Principal Component Analysis (PCA) to TWS, soil moisture and rainfall variations indentified the dominant annual water variability in the western, north-western, northern, and central regions, and the dominant seasonal variability in the

  10. Material growth and characterization for solid state devices

    NASA Technical Reports Server (NTRS)

    Collis, Ward J.; Abul-Fadl, A.; Iyer, S.

    1987-01-01

    During this period InGaAs and InGaAsP were grown on (100)InP by liquid phase electroepitaxy (LPEE). Results of the epitaxial growth of InGaAs on sputtered quartz masked substrates are presented. The resulting surface morphology can be related to the current density distribution near the edges of a masked pattern. The quaternary InGaAs was grown with compositions corresponding to 1.3 micron and 1.5 micron emission wavelengths. Growth rates were found to be linearly dependent upon current density, and a strong dependence upon composition was noted. These compositions lie in the miscibility gap region of the alloy phase diagram at the 645 C growth temperature. Growths were performed at 685 C to avoid the miscibility gap. Epilayers were characterized by photoluminescence, X-ray diffraction, secondary ion mass spectrometry, and Hall effect measurements. Aluminum oxide was deposited on silicon and InGaAs substrates for the characterization of this material as an insulator in a field effect transistor structure. It was determined that the results did not warrant further work with the deposition from an aluminum isopropoxide source. A metallographic vapor phase epitaxy system installation is nearing completion for use in hybrid III-V semiconductor epilayer growths.

  11. Growth and photosynthetic performance of five tree seedlings species in response to natural light regimes from the Central Pacific of Costa Rica.

    PubMed

    Guzmán, J Antonio; Cordero, Roberto A

    2013-09-01

    Environmental heterogeneity mostly dominated by differing light regimes affects the expression of phenotypic plasticity, which is important for plant growth and survival, especially in the forest understory. The knowledge about these responses to this heterogeneity is a key factor for forest restoration initiatives. In this study, we determine several phenotypic responses to contrasting light conditions in five native tree seedling species of La Cangreja National Park, Central Pacific of Costa Rica, four of them with threatened or relict populations. After 14 weeks at a medium gap condition (24% of full sun), seedlings were transferred and acclimated for 11 weeks to three different natural light regimes: large gap (LG), medium gap (MG) and small gap (SG), corresponding to 52%, 24%, 9% of the mean direct and indirect radiation at each site from full sun. Growth, biomass allocation and leaf gas exchange were measured after the acclimation period. Four species strongly reduced relative growth rate (RGR) in the lower light condition. Total biomass (TB) and RGR were different in Hymenaea courbaril and Platymiscium curiense. H. courbaril and Astronium graveolens had significant changes in the maximum assimilation rate, with a mean value in the LG of 11.02 and 7.70 micromolCO2/m2s, respectively. P. curuense showed the same trend and significant changes in RGR and biomass allocation. Aspidosperma myristicifolium and Plinia puriscalensis showed no adjustments to the light regimes in any of the measured variables. This study remarks the importance of determining the growth and physiological performance of these tree native species. It also demonstrates that the most threatened species are those with the less plastic responses to the light regimes, which stresses the difficult situation of their natural populations. This study highlights an urgent definition of the conservation and restoration needs of the degraded forests of the Costa Rican Central Pacific area, where these

  12. Cloacal and surface temperatures of tom turkeys exposed to different rearing temperature regimes during the first 12 weeks of growth.

    PubMed

    Mayes, S L; Strawford, M L; Noble, S D; Classen, H L; Crowe, T G

    2015-06-01

    Years of genetic selection have caused an increase in growth rate and market body mass in agricultural poultry species compared to earlier genetic strains, potentially altering their physiological requirements. The objective of this study was to expose Hybrid Converter tom turkeys on a weekly basis to the recommended rearing temperature regime (TCON: control) or 4°C below the recommended standard (TTRT: treatment) to determine their thermal responses. Once per week for 12 weeks, 12 turkeys were individually exposed to either TCON or TTRT for a 2-h period. Surface temperatures of the breast (TBREAST), wing (TWING), drumstick (TDRUM), head (THEAD), and shank (TSHANK) were measured at 20-min intervals using an infrared camera, while a thermal data logger measured the skin surface temperature under the wing (TLOGGER) at 30-s intervals. The cloacal temperature (TCORE) was measured using a medical thermometer at the start and end of the exposure period. Regardless of exposure temperature, the TBREAST (TCON: P<0.001 and TTRT: P<0.001), TWING (TCON: P<0.001 and TTRT: P<0.001), and TDRUM (TCON: P<0.001 and TTRT: P<0.001) decreased from weeks 4 to 6 and remained constant from weeks 1 to 3 and 8 to 12. THEAD was elevated in week 2 (TCON: P<0.001) or week 3 (TTRT: P<0.001), TSHANK increased slightly during week 3 for both TCON (P<0.001) and TTRT (P<0.001), and TLOGGER (TCON: P<0.001 and TTRT: P=0.001) and TCORE (TCON: P<0.001 and TTRT: P<0.001) were lower during the first week. Thereafter, THEAD, TSHANK, TLOGGER, and TCORE remained constant. Exposure to TTRT resulted in lower TBREAST, TWING, and TDRUM compared to TCON. Generally, THEAD, TSHANK, TLOGGER, and TCORE were not affected by the different exposure temperatures. The data demonstrated that the degree of thermal response expressed is dependent on the location of measurement, age, and exposure temperature. PMID:25589083

  13. Characterization of Minnesota lunar simulant for plant growth

    NASA Technical Reports Server (NTRS)

    Oglesby, James P.; Lindsay, Willard L.; Sadeh, Willy Z.

    1993-01-01

    Processing of lunar regolith into a plant growth medium is crucial in the development of a regenerative life support system for a lunar base. Plants, which are the core of such a system, produce food and oxygen for humans and, at the same time, consume carbon dioxide. Because of the scarcity of lunar regolith, simulants must be used to infer its properties and to develop procedures for weathering and chemical analyses. The Minnesota Lunar Simulant (MLS) has been identified to date as the best available simulant for lunar regolith. Results of the dissolution studies reveal that appropriately fertilized MLS can be a suitable medium for plant growth. The techniques used in conducting these studies can be extended to investigate the suitability of actual lunar regolith as a plant growth medium. Dissolution experiments were conducted using the MLS to determine its nutritional and toxicity characteristics for plant growth and to develop weathering and chemical analysis techniques. Two weathering regimes, one with water and one with dilute organic acids simulating the root rhizosphere microenvironment, were investigated. Elemental concentrations were measured using inductively-coupled-plasma (ICP) emission spectrometry and ion chromatography (IC). The geochemical speciation model, MINTEQA2, was used to determine the major solution species and the minerals controlling them. Acidification was found to be a useful method for increasing cation concentrations to meaningful levels. Initial results indicate that MLS weathers to give neutral to slightly basic solutions which contain acceptable amounts of the essential elements required for plant nutrition (i.e., potassium, calcium, magnesium, sulfur, zinc, sodium, silicon, manganese, copper, chlorine, boron, molybdenum, and cobalt). Elements that need to be supplemented include carbon, nitrogen, and perhaps phosphorus and iron. Trace metals in solution were present at nontoxic levels.

  14. Growth and Characterization of Bulk GeSi Solid Solutions

    NASA Technical Reports Server (NTRS)

    Ritter, Timothy M.

    1999-01-01

    In this work we have grown and characterized several GeSi samples in order to investigate the effects that Silicon concentration, applied magnetic field, and liquid encapsulation have on crystalline quality. Characterization techniques include NDIC microscopy and microprobe spectroscopy. Two samples were grown with a Silicon concentration of approximately 3% and are compared to previous growths having a Silicon fraction of approximately 5%. Growth conditions for one of these samples was varied with the presence of an external applied magnetic field to investigate the possibility of magnetic field damping. A comparison between these two ingots, and with previously grown material, revealed no clear improvement in sample crystalline quality. Three additional samples were grown using a CaCl2 liquid encapsulation technique that produced GeSi material with improved structural quality over previous samples. Comparisons to prior non-encapsulation grown material, details of our methodology, and suggestions for further improvements are discussed.

  15. High throughput growth and characterization of thin film materials

    NASA Astrophysics Data System (ADS)

    Mao, Samuel S.

    2013-09-01

    It usually takes more than 10 years for a new material from initial research to its first commercial application. Therefore, accelerating the pace of discovery of new materials is critical to tackling challenges in areas ranging from clean energy to national security. As discovery of new materials has not kept pace with the product design cycles in many sectors of industry, there is a pressing need to develop and utilize high throughput screening and discovery technologies for the growth and characterization of new materials. This article presents two distinctive types of high throughput thin film material growth approaches, along with a number of high throughput characterization techniques, established in the author's group. These approaches include a second-generation "discrete" combinatorial semiconductor discovery technology that enables the creation of arrays of individually separated thin film semiconductor materials of different compositions, and a "continuous" high throughput thin film material screening technology that enables the realization of ternary alloy libraries with continuously varying elemental ratios.

  16. In Situ Thin Film Growth and Characterization of Topological Dirac Semimetal Na3Bi

    NASA Astrophysics Data System (ADS)

    Hellerstedt, Jack; Edmonds, Mark; Liu, Chang; Ramakrishnan, Navneeth; Adam, Shaffique; Fuhrer, Michael

    The alkali pnictide Na3Bi is a three-dimensional Dirac semimetal possessing Dirac-like dispersions in kx, ky and kz, that has attracted recent interest as a condensed matter system for realizing the chiral anomaly. The high reactivity of sodium makes conventional synthesis and characterization extremely difficult: we circumvent this issue by combining thin film growth with low temperature STM and magnetotransport in one comprehensive UHV system. We have successfully grown Na3Bi on α-Al2O3 (0001) substrates, achieving low temperature mobilites in excess of 3,500 cm2/Vs and carrier densities as low as 5 × 10 12 cm-2. Perpendicular magnetoresistance up to 1T shows quadratic behavior with weak anti-localization at low field. Quantitative analysis of this data suggests that our samples are in a charge inhomogeneous regime reminiscent of charge puddling in graphene. JH, MTE and MSF are supported by MSF's ARC Laureate Fellowship (FL120100038).

  17. Tuning the Growth Pattern in 2D Confinement Regime of Sm2O3 and the Emerging Room Temperature Unusual Superparamagnetism

    PubMed Central

    Guria, Amit K.; Dey, Koushik; Sarkar, Suresh; Patra, Biplab K.; Giri, Saurav; Pradhan, Narayan

    2014-01-01

    Programming the reaction chemistry for superseding the formation of Sm2O3 in a competitive process of formation and dissolution, the crystal growth patterns are varied and two different nanostructures of Sm2O3 in 2D confinement regime are designed. Among these, the regular and self-assembled square platelets nanostructures exhibit paramagnetic behavior analogous to the bulk Sm2O3. But, the other one, 2D flower like shaped nanostructure, formed by irregular crystal growth, shows superparamagnetism at room temperature which is unusual for bulk paramagnet. It has been noted that the variation in the crystal growth pattern is due to the difference in the binding ability of two organic ligands, oleylamine and oleic acid, used for the synthesis and the magnetic behavior of the nanostructures is related to the defects incorporated during the crystal growth. Herein, we inspect the formation chemistry and plausible origin of contrasting magnetism of these nanostructures of Sm2O3. PMID:25269458

  18. [Characterization of growth-promoting rhizobacteria in Eucalyptus nitens seedlings].

    PubMed

    Angulo, Violeta C; Sanfuentes, Eugenio A; Rodríguez, Francisco; Sossa, Katherine E

    2014-01-01

    Rhizospheric and endophytic bacteria were isolated from the rizosphere and root tissue of Eucalyptus nitens. The objective of this work was to evaluate their capacity to promote growth in seedlings of the same species under greenhouse conditions. The isolates that improved seedling growth were identified and characterized by their capacity to produce indoleacetic acid (IAA), solubilize phosphates and increase 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. One hundred and five morphologically different strains were isolated, 15 of which promoted E. nitens seedling growth, significantly increasing the height (50%), root length (45%) as well as the aerial and root dry weight (142% and 135% respectively) of the plants. Bacteria belonged to the genus Arthrobacter, Lysinibacillus, Rahnella and Bacillus. Isolates A. phenanthrenivorans 21 and B. cereus 113 improved 3.15 times the emergence of E. nitens after 12 days, compared to control samples. Among isolated R. aquatilis, 78 showed the highest production of IAA (97.5±2.87 μg/ml) in the presence of tryptophan and the highest solubilizer index (2.4) for phosphorus, while B. amyloliquefaciens 60 isolate was positive for ACC deaminase activity. Our results reveal the potential of the studied rhizobacteria as promoters of emergence and seedling growth of E. nitens, and their possible use as PGPR inoculants, since they have more than one mechanism associated with plant growth promotion. PMID:25576419

  19. High resolution characterization of northwest Mediterranean coastal waters thermal regimes: To better understand responses of benthic communities to climate change

    NASA Astrophysics Data System (ADS)

    Bensoussan, Nathaniel; Romano, Jean-Claude; Harmelin, Jean-Georges; Garrabou, Joaquim

    2010-04-01

    In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature ( T) time series obtained during 1999-2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Réserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11-13 °C, and summer T mainly around 22-24 °C near surface to 18-20 °C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999, 2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1-2 °C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is

  20. Characterization of secondary phases in modified vertical bridgman growth czt

    SciTech Connect

    Duff, Martine

    2009-07-10

    CdZnTe or 'CZT' crystals are highly suitable for use as a room temperature based spectrometer for the detection and characterization of gamma radiation. Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. For example, various structural heterogeneities within the CZT crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SP) can have a negative impact on the detector performance. In this study, a CZT material was grown by the modified vertical Bridgman growth (MVB) method with zone leveled growth without excess Te in the melt. Visual observations of material from the growth of this material revealed significant voids and SP. Three samples from this material was analyzed using various analytical techniques to evaluate its electrical properties, purity and detector performance as radiation spectrometers and to determine the morphology, dimension and elemental/structural composition of one of the SP in this material. This material was found to have a high resistivity but poor radiation spectrometer performance. It had SP that were rich in polycrystalline aluminum oxide (Al{sub 2}O{sub 3}), metallic Te and polycrystalline CdZnTe and 15 to 50 {micro}m in diameter. Bulk elemental analyses of sister material from elsewhere in the boule did not contain high levels of Al so there is considerable elemental impurity heterogeneity within the boule from this growth.

  1. Growth and characterization of LuAs films and nanostructures

    SciTech Connect

    Krivoy, E. M.; Nair, H. P.; Crook, A. M.; Rahimi, S.; Maddox, S. J.; Salas, R.; Ferrer, D. A.; Dasika, V. D.; Akinwande, D.; Bank, S. R.

    2012-10-01

    We report the growth and characterization of nearly lattice-matched LuAs/GaAs heterostructures. Electrical conductivity, optical transmission, and reflectivity measurements of epitaxial LuAs films indicate that LuAs is semimetallic, with a room-temperature resistivity of 90 {mu}{Omega} cm. Cross-sectional transmission electron microscopy confirms that LuAs nucleates as self-assembled nanoparticles, which can be overgrown with high-quality GaAs. The growth and material properties are very similar to those of the more established ErAs/GaAs system; however, we observe important differences in the magnitude and wavelength of the peak optical transparency, making LuAs superior for certain device applications, particularly for thick epitaxially embedded Ohmic contacts that are transparent in the near-IR telecommunications window around 1.3 {mu}m.

  2. Direct Optical Characterization of Graphene Growth and Domains on Growth Substrates

    PubMed Central

    Jia, Chuancheng; Jiang, Jiaolong; Gan, Lin; Guo, Xuefeng

    2012-01-01

    We detailed a facile detection technique to optically characterize graphene growth and domains directly on growth substrates through a simple thermal annealing process. It was found that thermal annealing transformed the naked Cu to Cu oxides while keeping graphene and graphene-covered Cu intact. This increases the interference color contrast between Cu oxides and Cu, thus making graphene easily visible under an optical microscope. By using this simple method, we studied the factors that affect graphene nucleation and growth and achieved graphene domains with the domain size as large as ~100 μm. The concept of chemically making graphene visible is universal, as demonstrated by the fact that a solution process based on selective H2O2 oxidation has been developed to achieve the similar results in a shorter time. These techniques should be valuable for studies towards elucidating the parameters that control the grains, boundaries, structures and properties of graphene. PMID:23050091

  3. Growth and Characterization of Bismuth and Antimony Thin Films

    NASA Astrophysics Data System (ADS)

    Martinez, A.; Berrios, A. R.; Collazo, R.; Garcia, J. L.; Ducoudray, G. O.

    1996-03-01

    We have grown thin films of bismuth and antimony using hot wall epitaxy. The polycrystalline films were grown onto (111)-silicon substrates. The chemical integrity of the films was established using Auger electron spectroscopy. The crystallographical properties of the films were assessed using x-ray diffraction techniques. We will report on the results of these characterization efforts, as well as, on the growth apparatus and process. Work supported in part by NSWC-CRADA 93-01 and EPSCoR-NSF Grant EHR-9108775

  4. Characterizing the effects of ratchet growth on PBX 9502

    SciTech Connect

    Thompson, Darla Graff; Brown, Geoff W; Mang, Joseph T; De Luca, Racci; Patterson, Brian; Hagelberg, Stephanie

    2009-01-01

    Pressed composites of TATB (2,4,6-trinintro-1,3,5-benzenetriamine) undergo irreversible volume change when subjected to thermal cycling. Using micro x-ray computed tomography and ultra-small angle neutron scattering, we have characterized the micro-structure of as-pressed and ratchet grown specimens of PBX 9502, a TATB-based composite, thereby distinguishing the effects of ratchet growth from the effects of density alone. Porosity differences are shown to effect mechanical properties, presented here, with ongoing efforts to evaluate sensitivity and/or performance effects.

  5. Seasonal marine growth of Bristol Bay sockeye salmon (Oncorhynchus nerka) in relation to competition with Asian pink salmon (O. gorbuscho) and the 1977 ocean regime shift

    USGS Publications Warehouse

    Ruggerone, Gregory T.; Farley, E.; Nielsen, Jennifer L.; Hagen, P.

    2005-01-01

    Recent research demonstrated significantly lower growth and survival of Bristol Bay sockeye salmon (Oncorhynchus nerka) during odd-numbered years of their second or third years at sea (1975, 1977, etc.), a trend that was opposite that of Asian pink salmon (O. gorbuscha) abundance. Here we evaluated seasonal growth trends of Kvichak and Egegik river sockeye salmon (Bristol Bay stocks) during even- and odd-numbered years at sea by measuring scale circuli increments within each growth zone of each major salmon age group between 1955 and 2000. First year scale growth was not significantly different between odd- and even-numbered years, but peak growth of age-2. smolts was significantly higher than age-1. smolts. Total second and third year scale growth of salmon was significantly lower during odd- than during even-numbered years. However, reduced scale growth in odd-numbered years began after peak growth in spring and continued through summer and fall even though most pink salmon had left the high seas by late July (10-18% growth reduction in odd vs. even years). The alternating odd and even year growth pattern was consistent before and after the 1977 ocean regime shift. During 1977-2000, when salmon abundance was relatively great, sockeye salmon growth was high during specific seasons compared with that during 1955-1976, that is to say, immediately after entry to Bristol Bay, after peak growth in the first year, during the middle of the second growing season, and during spring of the third season. Growth after the spring peak in the third year at sea was relatively low during 1977-2000. We hypothesize that high consumption rates of prey by pink salmon during spring through mid-July of odd-numbered years, coupled with declining zooplankton biomass during summer and potentially cyclic abundances of squid and other prey, contributed to reduced prey availability and therefore reduced growth of Bristol Bay sockeye salmon during late spring through fall of odd

  6. Revealing the surface and bulk regimes of isothermal graphene growth on Ni with in situ kinetic measurements and modeling

    SciTech Connect

    Puretzky, Alexander A; Merkulov, Igor A; Rouleau, Christopher M; Eres, Gyula; Geohegan, David B

    2014-01-01

    In situ optical diagnostics are used to reveal the isothermal nucleation and growth mechanisms of graphene on Ni across a wide temperature range (560 C < T < 840 C) by chemical vapor deposition from single, sub-second pulses of acetylene. An abrupt, two-orders of magnitude change in growth times (~ 100s to 1s) is revealed at T = 680 C. Below and above this temperature, similar sigmoidal kinetics are measured and attributed to autocatalytic growth reactions but by two different mechanisms, surface assembly and dissolution/precipitation, respectively. These data are used to develop a simple and general kinetic model for graphene growth that includes the nucleation phase and includes the effects of carbon solubility in metals, describes delayed nucleation, and allows the interpretation of the competition between surface and bulk growth modes. The sharp transition in growth kinetics at T = 680 C is explained by a change in defect site density required for nucleation due to a transition in the carbon-induced mobility of the Ni surface. The easily-implemented optical reflectivity diagnostics and the simple kinetic model described here allow a pathway to optimize the growth of graphene on metals with arbitrary carbon solubility.

  7. Growth and invasive potential of Sapium sebiferum (Euphorbiaceae) within the coastal prairie region: the effects of soil and moisture regime

    USGS Publications Warehouse

    Barrilleaux, T.C.; Grace, J.B.

    2000-01-01

    The introduced tree Sapium sebiferum (Euphorbiaceae) is considered a serious threat to the preservation of the coastal prairie region of Louisiana and Texas, although it is currently uncommon in the western part of the region. The objective of this study was to evaluate the potential effects of location, soils, and available moisture on the growth and survival of S. sebiferum in coastal prairie. In a field experiment, S. sebiferum mortality was significantly greater at a western site than at central and eastern sites. The greatest mortality and least growth of surviving plants occurred on a soil from the western region, regardless of site. A greenhouse study also found that S. sebiferum growth was lowest on the western soil. Watering frequency significantly affected S. sebiferum growth, except on the western soil. Sapium sebiferum growth responded to both nitrogen and phosphorum additions for all soils. Soil analyses revealed the highest sand, sodium, and phosphorus contents, and much higher electrical conductivity in the western soil. It is concluded that the soil examined from the western region is unfavorable for S. sebiferum growth, though not to the extent to preclude S. sebiferum completely. Evidence suggests that soil salinity may be the primary cause of the poor S. sebiferum growth at the western site.

  8. Characterization of insulin-like growth factor I and epidermal growth factor receptors in meningioma

    SciTech Connect

    Kurihara, M.; Tokunaga, Y.; Tsutsumi, K.; Kawaguchi, T.; Shigematsu, K.; Niwa, M.; Mori, K. )

    1989-10-01

    Receptors for insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF) were localized and characterized in eight samples of human meningioma (four fibrous, two meningothelial, and two angioblastic types), using quantitative autoradiographic techniques. Effects of both growth factors on deoxyribonucleic acid (DNA) synthesis in the cultured meningioma cells were examined. High numbers of specific binding sites for both IGF-I and EGF were homogeneously present in tissue sections derived from fibrous and meningothelial types of meningiomas, whereas binding sites for these growth factors were not detectable in adjacent leptomeninges. While relatively large numbers of IGF-I binding sites were located in the wall of the intratumoral vasculature, the number of binding sites in the stromal component was lower in angioblastic-type meningiomas, including a low number of EGF binding sites detected only in the stromal portion. Scatchard analysis revealed the presence of a single class of high-affinity binding sites for both IGF-I and EGF in the meningiomas examined (dissociation constant (Kd) = 0.6 to 2.9 nM, and the maximum number of binding sites (Bmax) = 16 to 80 fmol/mg for IGF-I; and Kd = 0.6 to 4.0 nM, Bmax = 3 to 39 fmol/mg for EGF). Both growth factors increased the synthesis of DNA, in a dose-dependent manner, as measured by 3H-thymidine incorporation. The combination of IGF-I and EGF synergistically stimulated the synthesis of DNA, and the effects seen with 10% fetal bovine serum could be reproduced at a concentration of 10(-10) M. These observations can be interpreted to mean that both IGF-I and EGF may be involved in the growth modulation of meningiomas, possibly through paracrine or autocrine mechanisms.

  9. Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain.

    PubMed

    Bédard, Emilie; Boppe, Inès; Kouamé, Serge; Martin, Philippe; Pinsonneault, Linda; Valiquette, Louis; Racine, Jules; Prévost, Michèle

    2016-01-01

    Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila. PMID:27092528

  10. Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain

    PubMed Central

    Bédard, Emilie; Boppe, Inès; Kouamé, Serge; Martin, Philippe; Pinsonneault, Linda; Valiquette, Louis; Racine, Jules; Prévost, Michèle

    2016-01-01

    Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila. PMID:27092528

  11. Progress in characterizing submonolayer island growth: Capture-zone distributions, growth exponents, & hot precursors

    NASA Astrophysics Data System (ADS)

    Einstein, Theodore L.; Pimpinelli, Alberto; González, Diego Luis; Morales-Cifuentes, Josue R.

    2015-09-01

    In studies of epitaxial growth, analysis of the distribution of the areas of capture zones (i.e. proximity polygons or Voronoi tessellations with respect to island centers) is often the best way to extract the critical nucleus size i. For non-random nucleation the normalized areas s of these Voronoi cells are well described by the generalized Wigner distribution (GWD) Pβ(s) = asβ exp(-bs2), particularly in the central region 0.5 < s < 2 where data are least noisy. Extensive Monte Carlo simulations reveal inadequacies of our earlier mean field analysis, suggesting β = i + 2 for diffusion-limited aggregation (DLA). Since simulations generate orders of magnitude more data than experiments, they permit close examination of the tails of the distribution, which differ from the simple GWD form. One refinement is based on a fragmentation model. We also compare island-size distributions. We compare analysis by island-size distribution and by scaling of island density with flux. Modifications appear for attach-limited aggregation (ALA). We focus on the experimental system para-hexaphenyl on amorphous mica, comparing the results of the three analysis techniques and reconciling their results via a novel model of hot precursors based on rate equations, pointing out the existence of intermediate scaling regimes between DLA and ALA.

  12. Growth and characterization of doped LiF crystals

    NASA Astrophysics Data System (ADS)

    Khan, Sajid; Kim, H. J.; Rooh, Gul; Kim, Sunghwan

    2014-12-01

    Transparent and crack-free crystals of LiF: x ( x = Ca, Pb, Na, Tl) were successfully grown by using the Czochralski method. Growth parameters such as the pulling and the rotation rates were optimized. The grown crystals were characterized and compared by using X-ray luminescence. Tl- and Na-doped crystals showed better luminescence intensity than crystals with other dopants. Thermoluminescence (TL) glow curves were obtained to study the crystal defects in the grown samples. Activation energies were calculated from the TL glow curves. The temperature dependence of the light yield in the temperature range from 10 to 300 K under alpha particle excitation was also investigated. The light yield was found to be larger at low temperatures. Na- and Tl-doped crystals showed 35% and 20% increases in the light yield, respectively, at low temperatures as compared to room temperature.

  13. Synthesis, growth and characterization of cadmium manganese thiocyanate (CMTC) crystal

    NASA Astrophysics Data System (ADS)

    Paramasivam, P.; Raja, C. Ramachandra

    2011-09-01

    Single crystals of cadmium manganese thiocyanate, CdMn(SCN)4 (CMTC) have been successfully synthesized and grown by slow evaporation solution growth technique using water as solvent at room temperature. The crystal was characterized by different techniques for finding its suitability for device fabrications. From the single crystal XRD the crystal system was identified as tetragonal. The functional groups were identified from FTIR analysis. The optical studies have been carried out and found that the tendency of transmission observed from the specimen with respect to the wavelength of light is practically more suitable for the present trends in communication engineering. From the thermal analysis the decomposing temperature of the grown crystal is more significant when compared with the studies performed earlier.

  14. Synthesis, growth and characterization of cadmium manganese thiocyanate (CMTC) crystal.

    PubMed

    Paramasivam, P; Raja, C Ramachandra

    2011-09-01

    Single crystals of cadmium manganese thiocyanate, CdMn(SCN)4 (CMTC) have been successfully synthesized and grown by slow evaporation solution growth technique using water as solvent at room temperature. The crystal was characterized by different techniques for finding its suitability for device fabrications. From the single crystal XRD the crystal system was identified as tetragonal. The functional groups were identified from FTIR analysis. The optical studies have been carried out and found that the tendency of transmission observed from the specimen with respect to the wavelength of light is practically more suitable for the present trends in communication engineering. From the thermal analysis the decomposing temperature of the grown crystal is more significant when compared with the studies performed earlier. PMID:21640636

  15. Characterization of Mo/Si multilayer growth on stepped topographies

    SciTech Connect

    Boogaard, A. J. R. vcan den; Louis, E.; Zoethout, E.; Goldberg, K. A.; Bijkerk, F.

    2011-08-31

    Mo/Si multilayer mirrors with nanoscale bilayer thicknesses have been deposited on stepped substrate topographies, using various deposition angles. The multilayer morphology at the stepedge region was studied by cross section transmission electron microscopy. A transition from a continuous- to columnar layer morphology is observed near the step-edge, as a function of the local angle of incidence of the deposition flux. Taking into account the corresponding kinetics and anisotropy in layer growth, a continuum model has been developed to give a detailed description of the height profiles of the individual continuous layers. Complementary optical characterization of the multilayer system using a microscope operating in the extreme ultraviolet wavelength range, revealed that the influence of the step-edge on the planar multilayer structure is restricted to a region within 300 nm from the step-edge.

  16. Growth, crystalline perfection and characterization of benzophenone oxime crystal

    NASA Astrophysics Data System (ADS)

    Rajasekar, M.; Muthu, K.; Meenatchi, V.; Bhagavannarayana, G.; Mahadevan, C. K.; Meenakshisundaram, SP.

    Single crystals of benzophenone oxime (BPO) have been grown by slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the crystal belongs to monoclinic system and cell parameters are, a = 9.459 Å, b = 8.383 Å, c = 26.690 Å, v = 2115 Å3 and β = 92.807°. The structure and the crystallinity of the materials were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by FT-IR analysis. The TG/DSC studies reveal the purity of the material and the crystals are transparent in the entire visible region having a lower optical cut-off at ˜300 nm. The crystalline perfection was evaluated by high-resolution X-ray diffraction (HRXRD). The crystal is further characterized by Kurtz powder technique, dielectric studies and microhardness analysis.

  17. Growth and Characterization of Superconducting Indium Thin Films

    NASA Astrophysics Data System (ADS)

    Johnson-Steigelman, H.; Tahar, Mohammed

    2013-03-01

    Vacuum vapor deposition was used to produce nm - μm thick In films on glass slides and industrial and electronic substrates (doped Si, GaAs, and other elements). We report on the methods of synthesis, preparation, and characterization. Film thickness was controlled and determined using an in-situ four-point-probe during deposition on control samples. Samples manufactured alongside the control samples were then characterized using X-ray transmission for thickness determination, and diffraction for structure and morphology analysis. Transport measurements (Hall Effect and resistivity) were performed at room temperature (RT) to determine mobility. Resistivity measurements on portions of some samples were performed from RT down to below the superconducting transition, yielding consistent results for metallic behavior and transition temperature. Using the Matthiessen's rule and the Drude model for conduction in metals, one can determine the grain or crystallite size, which turned out an order of magnitude lower as compared to that obtained from X-ray diffraction, suggesting a preferred direction growth of In on glass.

  18. Acquisition of Single Crystal Growth and Characterization Equipment

    SciTech Connect

    Maple, M. Brian; Zocco, Diego A.

    2008-12-09

    Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As a result, many user facilities are not being used optimally. The number of proficient crystal growers is too small. In addition, insufficient attention is being paid to the enterprise of finding new and interesting materials, which is the driving force behind much of condensed matter research and, ultimately, technology. While a detailed assessment of this situation is clearly needed, enough evidence of a problem already exists to compel a general consensus that the situation must be addressed promptly. This final report describes the work carried out during the last four years in our group, in which a state-of-the-art single crystal growth and characterization facility was established for the study of novel oxides and intermetallic compounds of rare earth, actinide and transition metal elements. Research emphasis is on the physics of superconducting (SC), magnetic, heavy fermion (HF), non-Fermi liquid (NFL) and other types of strongly correlated electron phenomena in bulk single crystals. Properties of these materials are being studied as a function of concentration of chemical constituents, temperature, pressure, and magnetic field, which provide information about the electronic, lattice, and magnetic excitations at the root of various strongly correlated electron phenomena. Most importantly, the facility makes possible the investigation of material properties that can only be achieved in high quality bulk single crystals, including magnetic and transport phenomena, studies of the effects of disorder, properties in the clean limit, and spectroscopic and scattering

  19. Evaluation of vineyard growth under four irrigation regimes using vegetation and soil on-the-go sensors

    NASA Astrophysics Data System (ADS)

    Terrón, J. M.; Blanco, J.; Moral, F. J.; Mancha, L. A.; Uriarte, D.; Marques da Silva, J. R.

    2015-06-01

    Precision agriculture is a useful tool to assess plant growth and development in vineyards. The present study focused on spatial and temporal analysis of vegetation growth variability, in four irrigation treatments with four replicates. The research was carried out in a vineyard located in the southwest of Spain during the 2012 and 2013 growing seasons. Two multispectral sensors mounted on an all-terrain vehicle (ATV) were used in the different growing seasons/stages in order to calculate the vineyard normalized difference vegetation index (NDVI). Soil apparent electrical conductivity (ECa) was also measured up to 0.8 m soil depth using an on-the-go geophysical sensor. All measured data were analysed by means of principal component analysis (PCA). The spatial and temporal NDVI and ECa variations showed relevant differences between irrigation treatments and climatological conditions.

  20. Growth responses of wheat (Triticum aestivum L. var. HD 2329) exposed to ambient air pollution under varying fertility regimes.

    PubMed

    Singh, Anoop; Agrawal, S B; Rathore, Dheeraj

    2003-08-20

    The problem of urban air pollution has attracted special attention in India due to a tremendous increase in the urban population; motor vehicles vis a vis the extent of energy utilization. Field studies were conducted on wheat crops (Triticum aestivum L. var. HD 2329) by keeping the pot-grown plants in similar edaphic conditions at nine different sites in Allahabad City to quantify the effects of ambient air pollution levels on selected growth and yield parameters. Air quality monitoring was done at all the sites for gaseous pollutants viz. SO2, NO2, and O3. Various growth parameters (plant height, biomass, leaf area, NPP, etc.) showed adverse effects at sites receiving higher pollution load. Reduction in test weight and harvest index was found to be directly correlated with the levels of pollutant concentrations. The study clearly showed the negative impact of air pollution on periurban agriculture. PMID:12941977

  1. Growth, structure, and optical characterization of diluted magnetic semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Cooley, Benjamin Joseph

    ˜ 10 nm, with ˜ 15--20 nm being fairly common. Structural characterization done by transmission electron microscopy (TEM) shows that the long nanowires are largely single crystal, though often with many stacking faults, and tend to form in the wurtzite crystal structure with c-axis growth direction. Elemental analysis performed on individual nanowires using X-ray energy dispersive spectroscopy shows that Mn can be incorporated into Zn1-xMn xSe nanowires in high concentrations, up to x ˜ 0.6. Magneto-photoluminescence (magneto-PL) measurements of as-grown samples reveal substantial Zeeman shifts in the nearband edge luminescence, but only partial polarization, indicating the luminescence is originating in a nanostructured environment. Surprisingly, however, nearly all of the PL signal comes from the nanostructured undergrowth rather than the long nanowires, as shown from magneto-PL measurements of samples which were sonicated to remove the long nanowires. The next set of experiments covers ZnSe and (Zn,Mn)Se nanowires grown using a two-stage process. The substrates are prepared in a similar manner as the in the previous samples. The first stage of growth is carried out at lower than normal substrate temperature, which results in highly tapered nanoneedles with narrow tips (˜ 10 nm). The second stage of growth is performed under normal nanowire growth conditions, yielding narrow nanowires growing from the tips of the nanoneedles. These nanowires have far fewer defects than nanowires grown in a single stage process. Magneto-PL measurements carried out in a micro-PL system show many localized emitters and near band edge emission that shifts in a magnetic field. Sonicated samples gave similar results, indicating that the undergrowth is still responsible for much of the luminescence, even though there is much less undergrowth than in the single stage nanowires. Measurements of dispersed samples suggests that some of the luminescence may be coming from nanowires, but

  2. Characterization of Nanoaerosol Size Change During Enhanced Condensational Growth

    PubMed Central

    Longest, P. Worth; McLeskey, James T.; Hindle, Michael

    2010-01-01

    Increasing the size of nanoaerosols may be beneficial in a number of applications including filtration, particle size selection, and targeted respiratory drug delivery. A potential method to increase particle or droplet size is enhanced condensational growth (ECG), which involves combining the aerosol with saturated or supersaturated air. In this study, we characterize the ECG process in a model tubular geometry as a function of initial aerosol size (mean diameters – 150, 560 and 900 nm) and relative humidity conditions using both in vitro experiments and numerical modeling. Relative humidities (99.8 – 104%) and temperatures (25 – 39 °C) were evaluated that can safely be applied to either targeted respiratory drug delivery or personal aerosol filtration systems. For inlet saturated air temperatures above ambient conditions (30 and 39 °C), the initial nanoaerosols grew to a size range of 1000 – 3000 nm (1 – 3 μm) over a time period of 0.2 seconds. The numerical model results were generally consistent with the experimental findings and predicted final to initial diameter ratios of up to 8 after 0.2 s of humidity exposure and 14 at 1 s. Based on these observations, a respiratory drug delivery approach is suggested in which nanoaerosols in the size range of 500 nm are delivered in conjunction with a saturated or supersaturated air stream. The initial nanoaerosol size will ensure minimal deposition and loss in the mouth-throat region while condensational growth in the respiratory tract can be used to ensure maximal lung retention and to potentially target the site of deposition. PMID:20640054

  3. Growth and characterization of ferromagnetic nanostructures for device applications

    NASA Astrophysics Data System (ADS)

    Jugdersuren, Battogtokh

    Nanotechnology offers tremendous potential for future technology. A better understanding of ferromagnetism, half-metallicity and magnetostriction on the smallest scales are expected to improve technological performance. Processing and characterization of nanostructured materials, therefore, are central in modern solid state physics. One of the techniques to grow nanostructures is electrospinning which offers simplicity, low cost and flexibility. This dissertation focuses on functionally different colossal magnetoresistance strontium and calcium doped lanthanum manganites and magnetostrictive iron-gallium nanowires. We have tailored the conventional electrospinning method to grow high quality manganites and iron-gallium nanowires below 100 nm in diameter for the first time. We have shown that these ferromagnetic nanostructures can be grown parallel to one another for understanding the basic physics as well as for fabricating advanced device structures. Single nanowire devices were fabricated by electron-beam lithography. Details of the growth, morphology, structure and magnetic characterization, device fabrication and performance of the devices will be discussed in this thesis. Manganite nanowires have been grown by anodized alumina oxide template and by the pulsed laser deposition methods by other groups, nanowires grown from these techniques are difficult to use for device fabrication. Devices based on electrospun manganite and iron-gallium nanowires have shown improved electrical and magneto-transport properties. Half-metallic lanthanum-strontium manganite nanowires with 80--300 nm in diameters display enhanced magnetoresistance behavior at room temperature and the large magnetoresistance is exhibited at low magnetic field which will play an important role for creation of novel-next generation devices. Although inter-metallic, bulk iron-gallium is one of the highly attractive magnetostrictive materials, at nano level, it is very rarely studied due to difficulty

  4. Materials growth and characterization of thermoelectric and resistive switching devices

    NASA Astrophysics Data System (ADS)

    Norris, Kate J.

    In the 74 years since diode rectifier based radar technology helped the allied forces win WWII, semiconductors have transformed the world we live in. From our smart phones to semiconductor-based energy conversion, semiconductors touch every aspect of our lives. With this thesis I hope to expand human knowledge of semiconductor thermoelectric devices and resistive switching devices through experimentation with materials growth and subsequent materials characterization. Metal organic chemical vapor deposition (MOCVD) was the primary method of materials growth utilized in these studies. Additionally, plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD),ion beam sputter deposition, reactive sputter deposition and electron-beam (e-beam) evaporation were also used in this research for device fabrication. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Electron energy loss spectroscopy (EELS) were the primary characterization methods utilized for this research. Additional device and materials characterization techniques employed include: current-voltage measurements, thermoelectric measurements, x-ray diffraction (XRD), reflection absorption infra-red spectroscopy (RAIRS), atomic force microscopy (AFM), photoluminescence (PL), and raman spectroscopy. As society has become more aware of its impact on the planet and its limited resources, there has been a push toward developing technologies to sustainably produce the energy we need. Thermoelectric devices convert heat directly into electricity. Thermoelectric devices have the potential to save huge amounts of energy that we currently waste as heat, if we can make them cost-effective. Semiconducting thin films and nanowires appear to be promising avenues of research to attain this goal. Specifically, in this work we will explore the use of ErSb thin films as well as Si and InP nanowire networks for thermoelectric applications. First we will discuss the growth of

  5. A new parameter to characterize the charge transport regime in Ni/HfO2/Si-n+-based RRAMs

    NASA Astrophysics Data System (ADS)

    Villena, M. A.; Roldán, J. B.; González, M. B.; González-Rodelas, P.; Jiménez-Molinos, F.; Campabadal, F.; Barrera, D.

    2016-04-01

    In this work, a new parameter is defined to describe the charge transport regime and to understand the physics behind the operation of Ni/HfO2/Si-n+-based RRAMs. An extraction process of the parameter from experimental reset I-V curves is proposed. The new parameter allows to know the relative importance of the two main transport mechanisms involved in the charge conduction in the low resistance state of the device: a tunneling current through a potential barrier and an ohmic component. A complete simulation study on this issue is provided. Furthermore, the reset voltage can be estimated using this new parameter.

  6. Growth and nonlinear optical characterization of organic single crystal films

    NASA Astrophysics Data System (ADS)

    Zhou, Ligui

    1997-12-01

    Organic single crystal films are important for various future applications in photonics and integrated optics. The conventional method for inorganic crystal growth is not suitable for organic materials, and the high temperature melting method is not good for most organic materials due to decomposition problems. We developed a new method-modified shear method-to grow large area organic single crystal thin films which have exceptional nonlinear optical properties and high quality surfaces. Several organic materials (NPP, PNP and DAST) were synthesized and purified before the thin film crystal growth. Organic single crystal thin films were grown from saturated organic solutions using modified shear method. The area of single crystal films were about 1.5 cm2 for PNP, 1 cm2 for NPP and 5 mm2 for DAST. The thickness of the thin films which could be controlled by the applied pressure ranged from 1μm to 10 μm. The single crystal thin films of organic materials were characterized by polarized microscopy, x-ray diffraction, polarized UV-Visible and polarized micro-FTIR spectroscopy. Polarized microscopy showed uniform birefringence and complete extinction with the rotation of the single crystal thin films under crossed- polarization, which indicated high quality single crystals with no scattering. The surface orientation of single crystal thin films was characterized by x-ray diffraction. The molecular orientation within the crystal was further studied by the polarized UV-Visible and Polarized micro-FTIR techniques combined with the x-ray and polarized microscopy results. A Nd:YAG laser with 35 picosecond pulses at 1064nm wavelength was employed to perform the nonlinear optical characterization of the organic single crystal thin films. Two measurement techniques were used to study the crystal films: second harmonic generation (SHG) and electro-optic (EO) effect. SHG results showed that the nonlinear optical coefficient of NPP was 18 times that of LiNbO3, a standard

  7. Regime change?

    SciTech Connect

    Pilat, Joseph F.; Budlong-Sylvester, K. W.

    2004-01-01

    Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?

  8. Changes in leaf water relations, gas exchange, growth and flowering quality in potted geranium plants irrigated with different water regimes.

    PubMed

    Sánchez-Blanco, Ma Jesús; Alvarez, Sara; Navarro, Alejandra; Bañón, Sebastián

    2009-03-15

    Geranium plants are an important part of urban green areas but suffer from drought, especially when grown in containers with a limited volume of medium. In this experiment, we examined the response of potted geraniums to different irrigation levels. Geranium (Pelargoniumxhortorum L.) seedlings were grown in a growth chamber and exposed to three irrigation treatments, whereby the plants were irrigated to container capacity (control), 60% of the control (moderate deficit irrigation, MDI), or 40% of the control (severe deficit irrigation, SDI). Deficit irrigation was maintained for 2 months, and then all the plants were exposed to a recovery period of 112 month. Exposure to drought induced a decrease in shoot dry weight and leaf area and an increase in the root/shoot ratio. Height and plant width were significantly inhibited by the SDI, while flower color parameters were not affected by deficit treatment. The number of wilting and yellow leaves increased, coinciding with the increase in the number of inflorescences and open flowers. Deficit irrigation led to a leaf water potential of about -0.8MPa at midday, which could have caused an important decrease in stomatal conductance, affecting the photosynthetic rate (Pn). Chlorophyll fluorescence (Fvm) values of 0.80 in all treatments throughout the experiment demonstrate the lack of drought-induced damage to PSII photochemistry. Pressure-volume analysis revealed low osmotic adjustment values of 0.2MPa in the SDI treatment, accompanied by increases in the bulk tissue elastic modulus (epsilon, wall rigidity) and resulting in turgor loss at lower leaf water potential values (-1.38MPa compared with -1.0MPa for the control). Leaf water potential values throughout the experiment below those for Psitlp were not found at any sampling time. By the end of the recovery period, the leaf water potential, stomatal conductance and net photosynthesis had recovered. We infer from these results that moderate deficit irrigation in geranium

  9. Survival, development, and growth of Snake River fall Chinook salmon Embryos, Alevins, and Fry Exposed to Variable Thermal and Dissolved Oxygen Regimes

    SciTech Connect

    Geist, David R.; Abernethy, Cary S.; Hand, Kristine D.; Cullinan, Valerie I.; Chandler, James A.; Groves, Philip

    2006-11-01

    Fall Chinook salmon (Oncorhynchus tshawytscha) initiate spawning in the Hells Canyon reach of the Snake River, Idaho (rkm 240-397), at water temperatures above 16 C. This temperature exceeds the states of Idaho and Oregon water quality standards for salmonid spawning. These standards are consistent with results from studies of embryos exposed to a constant thermal regime, while salmon eggs in the natural environment are rarely exposed to a constant temperature regime. The objective of this study was to assess whether variable temperatures (i.e., declining after spawning) affected embryo survival, development, and growth of Snake River fall Chinook salmon alevins and fry. In 2003, fall Chinook salmon eggs were exposed to initial incubation temperatures ranging from 11-19 C in 2 C increments, and in 2004 eggs were exposed to initial temperatures of 13 C, 15 C, 16 C, 16.5 C, and 17 C. In both years, temperatures were adjusted downward approximately 0.2 C/day to mimic the thermal regime of the Snake River where these fish spawn. At 37-40 days post-fertilization, embryos were moved to a common exposure regime that followed the thermal profile of the Snake River through emergence. Mortality of fall Chinook salmon embryos increased markedly at initial incubation temperatures >17 C in both years. A logistic regression model estimated that a 50% reduction in survival from fertilization to emergence would occur at an initial incubation temperature of {approx}16 C. The laboratory results clearly showed a significant reduction in survival between 15 C and 17 C, which supported the model estimate. Results from 2004 showed a rapid decline in survival occurred between 16.5 C and 17 C, with no significant differences in survival at initial incubation temperatures <16.5 C. There were no significant differences across the range of initial temperature exposures for alevin and fry size at hatch and emergence. Differences in egg mass among females (notably 2003) most likely masked any

  10. Growth and characterization of diammonium copper disulphate hexahydrate single crystal

    SciTech Connect

    Siva Sankari, R.; Perumal, Rajesh Narayana

    2014-03-01

    Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a function of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function

  11. Effects of growth irradiance, nitrogen nutrition and watering regime on photosynthesis, leaf conductance and isoprene emission in leaves of Post Oak, Quercus stellata

    SciTech Connect

    Harley, P.; Archer, S.; Guenther, A. Texas A M Univ., College Station )

    1994-06-01

    Seedlings of Post Oak (Quercus stellata), the dominant woody species of oak savannas of east-central Texas, were grown outside in College Station, TX from April to November 1993. Plants were randomly placed in one cell of a 3 [times] 2 [times] 2 factorial experiment, employing 3 nitrogen fertilization (25, 100 and 225 ppm NH[sub 4]NO[sub 23]), 2 light levels (70% and 20% of full sun) and 2 watering regimes (to maintain 80-100% or 30-50% of field capacity). In November, net photosynthesis, leaf conductance and leaf isoprene emission rates at 30[degrees]C and PPFD=1000 [mu]mol m[sup [minus]2]s[sup [minus]1] were determined for two mature leaves on each of four plants from eight growth treatments and data were analyzed stastically. For plants grown under the lower watering regime, photosynthesis and isoprene emission increased with both increasing PPFD and nitrogen (effects significant at p<0.01). For plants grown at 70% full sun, effects of nitrogen treatment on photosynthesis, conductance and isoprene emission were significant (p<0.0001) while effects of watering treatment were not significant (p<0.2). Although watering treatment did not lead to significant differences between treatments, in a short-term drying experiment conducted on four plants, isoprene emissions increased through the drying period in previously well-watered plants, but decreased in previously droughted plants. Measurements were also made on two leaves to determine the effects of varying PPFD and temperature on rates of isoprene emission.

  12. Growth and characterization of group iiinitrides by migration-enhanced afterglow epitaxy

    NASA Astrophysics Data System (ADS)

    Gergova, Rositsa

    The work presented in this thesis investigates the growth and properties of group III- nitride semiconductors that were grown using the Migration Enhanced Afterglow Epitaxy (MEAglow) method. This work was to enhance the understanding of the MEAglow growth process towards the improvement of quality of the layers grown using this technique. The MEAglow technique applies the migration enhanced epitaxy method in a low pressure plasma-based CVD reactor, which has a potential of producing high quality epitaxial group III-nitride layers at relatively low growth temperatures on large deposition areas. The low temperature pulse growth in metal-rich regime, comprising the MME method was employed under growth pressures between 500 mTorr and 3000 mTorr. As the MME method up to this point has been used only for MBE systems, study of the impact of the growth pressure on the materials properties was necessary. In this work the pressure dependence was mapped to an existing surface phase diagram for MBE systems by calculating the number of nitrogen gas phase collisions and the metalorganic bombardment rate, for the specific to the prototype reactor parameters, to a first approximation. This was done in order to achieve an intermediate regime free of metal droplets for growth in metal-rich regime. High quality epitaxial InN layers were accomplished on extremely thin and smooth Ga2O3 buffer layers. These results indicate a potential for the application of Ga2O3 buffers in InN growth. The MEAglow InN layers were further optimized for growth on commercially available GaN buffer layers and excellent two-dimensional growth was achieved for layers grown under metal-rich conditions at 512 °C. Post-growth annealing studies were carried out for InN layers grown at temperatures below 400 °C to study the limiting processes of the removal of excess nitrogen, believed to be a dominant defect in InN films grown in plasma-based systems at very low temperatures. Variations in GaN stoichiometry

  13. A method for characterizing late-season low-flow regime in the upper Grand Ronde River Basin, Oregon

    USGS Publications Warehouse

    Kelly, Valerie J.; White, Seth

    2016-01-01

    This report describes a method for estimating ecologically relevant low-flow metrics that quantify late‑season streamflow regime for ungaged sites in the upper Grande Ronde River Basin, Oregon. The analysis presented here focuses on sites sampled by the Columbia River Inter‑Tribal Fish Commission as part of their efforts to monitor habitat restoration to benefit spring Chinook salmon recovery in the basin. Streamflow data were provided by the U.S. Geological Survey and the Oregon Water Resources Department. Specific guidance was provided for selection of streamgages, development of probabilistic frequency distributions for annual 7-day low-flow events, and regionalization of the frequency curves based on multivariate analysis of watershed characteristics. Evaluation of the uncertainty associated with the various components of this protocol indicates that the results are reliable for the intended purpose of hydrologic classification to support ecological analysis of factors contributing to juvenile salmon success. They should not be considered suitable for more standard water-resource evaluations that require greater precision, especially those focused on management and forecasting of extreme low-flow conditions.

  14. Sequential growth of deformation bands in carbonate grainstones in the hangingwall of an active growth fault: Implications for deformation mechanisms in different tectonic regimes

    NASA Astrophysics Data System (ADS)

    Rotevatn, Atle; Thorsheim, Elin; Bastesen, Eivind; Fossmark, Heidi S. S.; Torabi, Anita; Sælen, Gunnar

    2016-09-01

    Deformation bands in porous sandstones have been extensively studied for four decades, whereas comparatively less is known about deformation bands in porous carbonate rocks, particularly in extensional settings. Here, we investigate porous grainstones of the Globigerina Limestone Formation in Malta, which contain several types of deformation bands in the hangingwall of the Maghlaq Fault: (i) bed-parallel pure compaction bands (PCB); (ii) pressure solution-dominated compactive shear bands (SCSB) and iii) cataclasis-dominated compactive shear bands (CCSB). Geometric and kinematic analyses show that the bands formed sequentially in the hangingwall of the evolving Maghlaq growth fault. PCBs formed first due to fault-controlled subsidence and vertical loading; a (semi-)tectonic control on PCB formation is thus documented for the first time in an extensional setting. Pressure solution (dominating SCSBs) and cataclasis (dominating CCSBs) appear to have operated separately, and not in concert. Our findings therefore suggest that, in some carbonate rocks, cataclasis within deformation bands may develop irrespective of whether pressure solution processes are involved. We suggest this may be related to stress state, and that whereas pressure solution is a significant facilitator of grain size reduction in contractional settings, grain size reduction within deformation bands in extensional settings is less dependent on pressure solution processes.

  15. Lead-lag cross-sectional structure and detection of correlated anticorrelated regime shifts: Application to the volatilities of inflation and economic growth rates

    NASA Astrophysics Data System (ADS)

    Zhou, Wei-Xing; Sornette, Didier

    2007-07-01

    We have recently introduced the “thermal optimal path” (TOP) method to investigate the real-time lead-lag structure between two time series. The TOP method consists in searching for a robust noise-averaged optimal path of the distance matrix along which the two time series have the greatest similarity. Here, we generalize the TOP method by introducing a more general definition of distance which takes into account possible regime shifts between positive and negative correlations. This generalization to track possible changes of correlation signs is able to identify possible transitions from one convention (or consensus) to another. Numerical simulations on synthetic time series verify that the new TOP method performs as expected even in the presence of substantial noise. We then apply it to investigate changes of convention in the dependence structure between the historical volatilities of the USA inflation rate and economic growth rate. Several measures show that the new TOP method significantly outperforms standard cross-correlation methods.

  16. Epitaxial Growth and Characterization of Silicon Carbide Films

    SciTech Connect

    Dhanaraj,G.; Dudley, M.; Chen, Y.; Ragothamachar, B.; Wu, B.; Zhang, H.

    2006-01-01

    Silicon carbide (SiC) epitaxial layers have been grown in a chemical vapor deposition (CVD) system designed and fabricated in our laboratory. Silicon tetrachloride-propane as well as silane-propane were used as precursor gases. The hot zone was designed based on simulation by using numerical modeling. Growth rates up to 200 {mu}m could be achieved. A new growth-assisted hydrogen etching was developed to show the distribution of the micropipes present in the substrate. Higher growth rate was observed on off-axis (0 0 0 1) 4 H SiC compared to the on-axis (0 0 0 1) wafer and growth mechanism was explained.

  17. Novel nanostructured thin film heterostructures: Growth, nanoscale characterization and properties

    NASA Astrophysics Data System (ADS)

    Chugh, Amit

    During my graduate study, I have been involved in the growth of new nano heterostructures grown by Pulsed Laser Deposition and by Laser MBE with the emphasis on understanding the thin film growth process by a new paradigm of Domain Matching Epitaxy (DME) and to integrate them on substrates like silicon, sapphire and new metallic substrates like Ni with exciting technological applications. The DME involves matching of integral multiples of lattice planes (diffracting as well as nondiffracting) between the film and the substrate, and this matching could be different in different directions. The idea of matching planes is derived from the basic fact that during thin film growth lattice relaxation involves generation of dislocations whose Burgers vectors correspond to missing or extra planes, rather than lattice constants. In the DME framework, the conventional lattice matching epitaxy (LME) becomes a special case where matching of lattice constants results from matching of lattice planes with a relatively small misfit of less than 7-8%. In large lattice mismatch systems, epitaxial growth of thin films is possible by matching of domains where integral multiples of lattice planes match across the interface. The work done in my doctoral study is divided into two main segments, (a) Growth of layered nanostructures and (b) growth of nanostructured composite thin films. The three systems studied under the first segment are (1) Growth of epitaxial self-aligned insulating films on metals (Cu) and its integration with Si (100). (2) Growth and integration of LSMO with Si (100). (3) Growth of Si on Ni substrates (highly textured) with TiN as a buffer layer. The heterostructures studied under the second part are (1) Role of Self-assembled Gold Nanodots in Improving the Electrical and Optical Characteristics of Zinc Oxide Films and (2) Growth of high quality epitaxial ZnO-Pt Nanocomposite and ZnO/Pt, Nanolayer Structures on Sapphire (0001). The epitaxial growth of these

  18. Growth and characterization of graphene on CuNi substrates

    NASA Astrophysics Data System (ADS)

    Tyagi, Parul

    Graphene is a single layer of sp2 bonded carbon atoms that crystallizes in the honeycomb structure. Because of its true two-dimensional structure, it has very unique electrical properties, including a very high carrier mobility that is symmetric for holes and electrons. To realize these unique properties, it is important to develop a method for growing graphene films with uniform thickness and low defect density. One of the most popular methods of growth is by chemical vapor deposition on Cu substrates, because it is self-limited. However many applications require the growth of graphene films that are more than one atomic layer thick. In this research project, the growth of graphene on CuNi substrates has been studied. The presence of Ni in the alloy results in an increase in the catalytic activity of the surface. This results in lower deposition pressures than for pure Cu and also increases the carbon solubility, which allows the growth of films that are more than one atomic layer thick. Two types of substrates were used for the growth of the graphene films: CuNi foils with an alloy composition of 90:10 and 70:30 Cu-Ni by weight and a CuNi(111) single crystal with a composition of 90:10 by weight. For the 70:30 substrates, it was very difficult to control the graphene thickness. On the other hand, the controlled growth of graphene films that were more than one layer thick was achieved on the 90:10 substrates. The growth morphology and the crystal structure of graphene grown on the CuNi(111) surface was determined by performing these studies in an ultra-high vacuum chamber to achieve very high purity conditions. The low energy electron diffraction analysis of the graphene films showed that the graphene films always nucleated in more than one rotational orientation with respect to the substrate. The growth was achieved at temperatures as low as 500 °C, which is much lower in temperature than for Cu substrates. Scanning electron microscopy analysis of the graphene

  19. In-situ TEM characterization of Copper Growth

    NASA Astrophysics Data System (ADS)

    Shelberg, Daniel T.

    In-situ liquid experiments in the transmission electron microscope (TEM) allow dynamic phenomena to be imaged at the nanoscale. This opens the opportunity to view electrochemical depositions at the nano scale in real time. However, there are a number of issues regarding in situ imaging that prevent a straightforward approach. This thesis addresses two issues regarding in-situ experiments; the fabrication of electron transparent windows and the nucleation of a metal from an electrolyte as a result of beam damage. Silicon chips that were 2.6mm x 2.6mm with 50mum x 50mum windows consisting of 50nm S3N 4 were fabricated with the goal of minimizing fabrication complexity at a cost significantly below commercial prices. These silicon nitride windows were used to sandwich a small volume of CuSO4 solution and observe copper nucleation as a result of the radiolysis damage of water due to the electron beam. Scanning transmission electron microscopy (STEM) was used to image growth, and reducing species are shown to diffuse on the order of hundreds of nanometers in solution. Copper nanoparticle growth was compared to Oswald ripening, and diffusion limited growth was observed at high electron dose rates. The diffusion limited growth was suppressed and led to a slower growth rate, with a calculated diffusion coefficient for Cu 2+ of 2 x 10--10 m2/s. Low electron dose rates corresponding to low magnifications in STEM yielded kinetic limited or mixed growth and yielded faceted nanoparticles. Atomic resolution was achieved in copper film deposited at low magnifications, and lattice fringes corresponding to the copper <111> were observed.

  20. Characterization and estrogen regulation of uterine growth factor activity

    SciTech Connect

    Beck, C.A.

    1988-01-01

    Acid extracts of rat, bovine and rabbit uterus stimulated glucose transport, measured by phosphorylation of 2-deoxyglucose and DNA synthesis, measured by {sup 3}H-thymidne incorporation, in uterine tumor cells and in primary cultures of rat uterine cells. The stimulation of glucose transport was of the same magnitude and followed the same time course as estradiol stimulation in vivo. Uteri from estradiol-treated rat uteri contained 4 times more glucose transport-stimulating activity as control uteri. DNA synthetic activity in rat uterine homogenates was elevated 3-fold within 18-24 h after estradiol injection. Gel filtration showed molecular weight heterogeneity with activity eluting between 10-30 kDA. Both activities were acid and heat stable, were reduced by trypsin but not by dextran-coated charcoal. The effect of purified growth factors on DNA synthesis in primary cultures of rat uterine cells was examined. Epidermal growth factor (EGF), basic fibroblasts growth factor (bFGF), and transforming growth factor-{beta} (TGF{beta}) had no effect on {sup 3}H-thymidine incorporation.

  1. Characterization of Alcohol-induced Filamentous Growth in Saccharomyces cerevisiae

    PubMed Central

    Lorenz, Michael C.; Cutler, N. Shane; Heitman, Joseph

    2000-01-01

    Diploid cells of the budding yeast Saccharomyces cerevisiae starved for nitrogen differentiate into a filamentous growth form. Poor carbon sources such as starches can also stimulate filamentation, whereas haploid cells undergo a similar invasive growth response in rich medium. Previous work has demonstrated a role for various alcohols, by-products of amino acid metabolism, in altering cellular morphology. We found that several alcohols, notably isoamyl alcohol and 1-butanol, stimulate filamentous growth in haploid cells in which this differentiation is normally repressed. Butanol also induces cell elongation and changes in budding pattern, leading to a pseudohyphal morphology, even in liquid medium. The filamentous colony morphology and cell elongation require elements of the pheromone-responsive MAPK cascade and TEC1, whereas components of the nutrient-sensing machinery, such as MEP2, GPA2, and GPR1, do not affect this phenomenon. A screen for 1-butanol–insensitive mutants identified additional proteins that regulate polarized growth (BUD8, BEM1, BEM4, and FIG1), mitochondrial function (MSM1, MRP21, and HMI1), and a transcriptional regulator (CHD1). Furthermore, we have also found that ethanol stimulates hyperfilamentation in diploid cells, again in a MAPK-dependent manner. Together, these results suggest that yeast may sense a combination of nutrient limitation and metabolic by-products to regulate differentiation. PMID:10637301

  2. Effect of controlled inoculation with specific mycorrhizal fungi from the urban environment on growth and physiology of containerized shade tree species growing under different water regimes.

    PubMed

    Fini, Alessio; Frangi, Piero; Amoroso, Gabriele; Piatti, Riccardo; Faoro, Marco; Bellasio, Chandra; Ferrini, Francesco

    2011-11-01

    The aim of this work was to evaluate the effects of selected mycorrhiza obtained in the urban environment on growth, leaf gas exchange, and drought tolerance of containerized plants growing in the nursery. Two-year-old uniform Acer campestre L., Tilia cordata Mill., and Quercus robur L. were inoculated with a mixture of infected roots and mycelium of selected arbuscular (maple, linden) and/or ectomycorrhiza (linden, oak) fungi and grown in well-watered or water shortage conditions. Plant biomass and leaf area were measured 1 and 2 years after inoculation. Leaf gas exchange, chlorophyll fluorescence, and water relations were measured during the first and second growing seasons after inoculation. Our data suggest that the mycelium-based inoculum used in this experiment was able to colonize the roots of the tree species growing in the nursery. Plant biomass was affected by water shortage, but not by inoculation. Leaf area was affected by water regime and, in oak and linden, by inoculation. Leaf gas exchange was affected by inoculation and water stress. V(cmax) and J(max) were increased by inoculation and decreased by water shortage in all species. F(v)/F(m) was also generally higher in inoculated plants than in control. Changes in PSII photochemistry and photosynthesis may be related to the capacity of inoculated plants to maintain less negative leaf water potential under drought conditions. The overall data suggest that inoculated plants were better able to maintain physiological activity during water stress in comparison to non-inoculated plants. PMID:21472449

  3. Characterization of the intragranular water regime within subsurface sediments: Pore volume, surface area, and mass transfer limitations

    USGS Publications Warehouse

    Hay, M.B.; Stoliker, D.L.; Davis, J.A.; Zachara, J.M.

    2011-01-01

    Although "intragranular" pore space within grain aggregates, grain fractures, and mineral surface coatings may contain a relatively small fraction of the total porosity within a porous medium, it often contains a significant fraction of the reactive surface area, and can thus strongly affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment procedure using tritiated water as a high-resolution diffusive tracer to characterize the intragranular pore space. The method was tested using uranium-contaminated sediments from the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site (Washington). Sediments were contacted with tracers in artificial groundwater, followed by a replacement of bulk solution with tracer-free groundwater and the monitoring of tracer release. From these data, intragranular pore volumes were calculated and mass transfer rates were quantified using a multirate first-order mass transfer model. Tritium-hydrogen exchange on surface hydroxyls was accounted for by conducting additional tracer experiments on sediment that was vacuum dried after reaction. The complementary ("wet" and "dry") techniques allowed for the simultaneous determination of intragranular porosity and surface area using tritium. The Hanford 300A samples exhibited intragranular pore volumes of ???1% of the solid volume and intragranular surface areas of ???20%-35% of the total surface area. Analogous experiments using bromide ion as a tracer yielded very different results, suggesting very little penetration of bromide into the intragranular porosity. Copyright 2011 by the American Geophysical Union.

  4. Characterization of the intragranular water regime within subsurface sediments: pore volume, surface area, and mass transfer limitations

    USGS Publications Warehouse

    Hay, Michael B.; Stoliker, Deborah L.; Davis, James A.; Zachara, John M.

    2011-01-01

    Although "intragranular" pore space within grain aggregates, grain fractures, and mineral surface coatings may contain a relatively small fraction of the total porosity within a porous medium, it often contains a significant fraction of the reactive surface area, and can thus strongly affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment procedure using tritiated water as a high-resolution diffusive tracer to characterize the intragranular pore space. The method was tested using uranium-contaminated sediments from the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site (Washington). Sediments were contacted with tracers in artificial groundwater, followed by a replacement of bulk solution with tracer-free groundwater and the monitoring of tracer release. From these data, intragranular pore volumes were calculated and mass transfer rates were quantified using a multirate first-order mass transfer model. Tritium-hydrogen exchange on surface hydroxyls was accounted for by conducting additional tracer experiments on sediment that was vacuum dried after reaction. The complementary ("wet" and "dry") techniques allowed for the simultaneous determination of intragranular porosity and surface area using tritium. The Hanford 300A samples exhibited intragranular pore volumes of ~1% of the solid volume and intragranular surface areas of ~20%–35% of the total surface area. Analogous experiments using bromide ion as a tracer yielded very different results, suggesting very little penetration of bromide into the intragranular porosity.

  5. Temperature control and calibration issues in the growth, processing and characterization of electronic materials

    NASA Technical Reports Server (NTRS)

    Wilson, B. A.

    1989-01-01

    The temperature control and calibration issues encountered in the growth, processing, and characterization of electronic materials are summarized. The primary problem area is identified as temperature control during epitaxial materials growth. While qualitative thermal measurements are feasible and reproducibility is often achievable within a given system, absolute calibration is essentially impossible in many cases, precluding the possibility of portability from one system to another. The procedures utilized for thermal measurements during epitaxial growth are described, and their limitations discussed.

  6. Characterization of the intragranular water regime within subsurface sediments: Pore volume, surface area, and mass transfer limitations

    SciTech Connect

    Hay, Michael B.; Stoliker, Deborah L.; Davis, James A.; Zachara, John M.

    2011-10-29

    Although 'intragranular' pore space within grain aggregates, grain fractures, and mineral 24 surface coatings may contain a relatively small fraction of the total porosity within a porous 25 medium, it often contains a significant fraction of the reactive surface area, and can thus strongly 26 affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment 27 procedure using tritium and bromide as high-resolution diffusive tracers to characterize the 28 intragranular pore space. The method was tested using uranium-contaminated sediments from 29 the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site 30 (Washington State, USA). Sediments were contacted with tracers in artificial groundwater, 31 followed by replacement of bulk solution with tracer-free groundwater and monitoring of tracer 32 release. From these data, intragranular pore volumes were calculated and mass transfer rates 33 were quantified using a multirate first-order mass transfer model. Tritium-hydrogen exchange 34 on surface hydroxyls was accounted for by conducting additional tracer experiments on sediment 35 that was vacuum dried after reaction. The complementary ('wet' and 'dry') techniques allowed 36 for the simultaneous determination of intragranular porosity and surface area using tritium. The 37 Hanford 300A samples exhibited intragranular pore volumes of {approx}1% of the solid volume and 38 intragranular surface areas of {approx}20-30% of the total surface area. Comparison with N2 gas 39 adsorption suggests that this pore space includes both 'micropores' (< 2 nm diameter) and 40 'mesopores' (> 2 nm). Intragranular porosity estimates obtained using bromide were 41 significantly smaller, likely due to anion exclusion of Br- from pores with negatively charged 42 surfaces.

  7. Material growth and characterization for solid state devices

    NASA Technical Reports Server (NTRS)

    Collis, Ward J.; Abul-Fadl, Ali; Iyer, Shanthi

    1988-01-01

    During the period of this research grant, the process of liquid phase electroepitaxy (LPEE) was used to grow ternary and quaternary alloy III-V semiconductor thin films. Selective area growth of InGaAs was performed on InP substrates using a patterned sputtered quartz or spin-on glass layer. The etch back and growth characteristics with respect to substrate orientation were investigated. The etch back behavior is somewhat different from wet chemical etching with respect to the sidewall profiles which are observed. LPEE was also employed to grow epitaxial layers of InGaAsP alloys on InP substrates. The behavior of Mn as an acceptor dopant was investigated with low temperature Hall coefficient and photoluminescence measurements. A metal-organic vapor phase epitaxy system was partially complete within the grant period. This atmospheric pressure system will be used to deposit III-V compound and alloy semiconductor layers in future research efforts.

  8. Growth and characterization of ammonium acid phthalate single crystals

    NASA Astrophysics Data System (ADS)

    Arunkumar, A.; Ramasamy, P.

    2013-04-01

    Ammonium acid phthalate (AAP) has been synthesized and single crystals were grown by slow evaporation solution growth technique. The unit cell parameters were confirmed by single crystal X-ray diffraction analysis and it belongs to orthorhombic system with the space group of Pcab. The high resolution X-ray diffraction studies revealed the crystalline perfection of the grown crystal. The various functional groups of AAP were identified by FT-IR and Raman spectral analyses. Thermal stability of the grown crystals was studied by TGA/DTA. The optical properties of the grown crystals were analyzed by UV-Vis-NIR and photoluminescence spectral studies. The mechanical property of the grown crystal was studied by Vickers microhardness measurement. The growth features of AAP were analyzed by chemical etching.

  9. Single crystal growth and characterization of URu2Si2

    NASA Astrophysics Data System (ADS)

    Haga, Yoshinori; Matsuda, Tatsuma D.; Tateiwa, Naoyuki; Yamamoto, Etsuji; Ōnuki, Yoshichika; Fisk, Zachary

    2014-11-01

    We review recent progress in single crystal growth and study of electronic properties in ?. Czocharalski pulling, using purified uranium metal and subsequent annealing under ultra-high vacuum, is successfully applied to this compound, and it yields the highest residual resistivity ratio. These high-quality single crystals allow us to investigate Fermi surfaces using quantum oscillation and to make detailed transport measurements at low temperature.

  10. Morphologic characterization of osteosarcoma growth on the chick chorioallantoic membrane

    PubMed Central

    2010-01-01

    Background The chick chorio-allantoic membrane (CAM) assay is a commonly used method for studying angiogenic or anti-angiogenic activities in vivo. The ease of access allows direct monitoring of tumour growth by biomicroscopy and the possibility to screen many samples in an inexpensive way. The CAM model provides a powerful tool to study effects of molecules, which interfere with physiological angiogenesis, or experimental tumours derived from cancer cell lines. We therefore screened eight osteosarcoma cell lines for their ability to form vascularized tumours on the CAM. Findings We implanted 3-5 million cells of human osteosarcoma lines (HOS, MG63, MNNG-HOS, OST, SAOS, SJSA1, U2OS, ZK58) on the CAM at day 10 of embryonic development. Tumour growth was monitored by in vivo biomicroscopy at different time points and tumours were fixed in paraformaldehyde seven days after cell grafting. The tissue was observed, photographed and selected cases were further analyzed using standard histology. From the eight cell lines the MNNG-HOS, U2OS and SAOS were able to form solid tumours when grafted on the CAM. The MNNG-HOS tumours showed the most reliable and consistent growth and were able to penetrate the chorionic epithelium, grow in the CAM stroma and induce a strong angiogenic response. Conclusions Our results show that the CAM assay is a useful tool for studying osteosarcoma growth. The model provides an excellent alternative to current rodent models and could serve as a preclinical screening assay for anticancer molecules. It might increase the speed and efficacy of the development of new drugs for the treatment of osteosarcoma. PMID:20202196

  11. Growth and characterization of metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Henz, J.; Ospelt, M.; Von Känel, H.

    1989-04-01

    Thanks to recent advances in the growth of CoSi 2-layers on Si(111) it has become possible for the first time to fabricate metal/semiconductor superlattices. This is achieved by a combination of solid phase epitaxy (SPE) and molecular beam epitaxy (MBE). We briefly explain the growth of thin ( < 100 Å) type B oriented (i.e. rotated by 180° with respect to the substrate) CoSi 2 layers. We show the effect of the two different surface structures of CoSi 2 on the morphology of the films. Silicon with a reasonable crystal quality can be grown on top of CoSi 2 by using low substrate temperatures for the first few monolayers of growth. We always find the orientation of Si to be the same as the one of the underlying suicide, when the latter is of high quality. Superlattices of CoSi 2 and Si have two periods, one being given by the different materials and the other by the alternating crystal orientations. We show some TEM cross section images as well as first X-ray investigations of these structures.

  12. Growth and Characterization of Graphene-Boron Nitride Heterostructures

    NASA Astrophysics Data System (ADS)

    Sutter, Peter

    2012-02-01

    Graphene has been used to explore the fascinating properties of two-dimensional sp^2 carbon, and shows great promise for applications. Heterostructures of graphene (G) and hexagonal boron nitride (h-BN) have the potential for extended functionality, e.g., providing high carrier mobilities in graphene devices supported on h-BN and giving rise to emergent electronic behavior near in-plane G/h-BN junctions. While significant progress has been made recently in separate graphene and boron nitride growth on transition metals, the controlled synthesis of high-quality G/h-BN heterostructures poses new challenges. We discuss the fundamental growth mechanisms underlying the synthesis of G/h-BN heterostructures, studied by a combination of in-situ surface microscopy methods. Real-time low-energy electron microscopy (LEEM) provides a mesoscale view of the nucleation and growth of h-BN in the presence of graphene, and vice-versa. LEEM imaging together with diffraction and angle resolved photoemission spectroscopy (micro-ARPES) gives insight into the interaction between graphene and h-BN. Scanning tunneling microscopy has been used to probe intermixing and the atomic-scale structure of interfacial boundaries. Combining real-time and atomic-resolution imaging, we identify successful approaches for achieving atomically sharp G/h-BN junctions.

  13. Kinematics of cardiac growth: In vivo characterization of growth tensors and strains

    PubMed Central

    Tsamis, Alkiviadis; Cheng, Allen; Nguyen, Tom C.; Langer, Frank; Miller, D. Craig; Kuhl, Ellen

    2012-01-01

    Progressive growth and remodeling of the left ventricle are part of the natural history of chronic heart failure and strong clinical indicators for survival. Accompanied by changes in cardiac form and function, they manifest themselves in alterations of cardiac strains, fiber stretches, and muscle volume. Recent attempts to shed light on the mechanistic origin of heart failure utilize continuum theories of growth to predict the maladaptation of the heart in response to pressure or volume overload. However, despite a general consensus on the representation of growth through a second order tensor, the precise format of this growth tensor remains unknown. Here we show that infarct-induced cardiac dilation is associated with a chronic longitudinal growth, accompanied by a chronic thinning of the ventricular wall. In controlled in vivo experiments throughout a period of seven weeks, we found that the lateral left ventricular wall adjacent to the infarct grows longitudinally by more than 10%, thins by more than 25%, lengthens in fiber direction by more than 5%, and decreases its volume by more than 15%. Our results illustrate how a local loss of blood supply induces chronic alterations in structure and function in adjacent regions of the ventricular wall. We anticipate our findings to be the starting point for a series of in vivo studies to calibrate and validate constitutive models for cardiac growth. Ultimately, these models could be useful to guide the design of novel therapies, which allow us to control the progression of heart failure. PMID:22402163

  14. Second harmonic chalcone crystal: Synthesis, growth and characterization

    NASA Astrophysics Data System (ADS)

    D'silva, E. D.; Narayan Rao, D.; Philip, Reji; Butcher, Ray J.; Rajnikant; Dharmaprakash, S. M.

    2011-05-01

    The novel nonlinear optical chalcone derivative (2 E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.

  15. Characterizing growth patterns in longitudinal MRI using image contrast

    NASA Astrophysics Data System (ADS)

    Vardhan, Avantika; Prastawa, Marcel; Vachet, Clement; Piven, Joseph; Gerig, Guido

    2014-03-01

    Understanding the growth patterns of the early brain is crucial to the study of neuro-development. In the early stages of brain growth, a rapid sequence of biophysical and chemical processes take place. A crucial component of these processes, known as myelination, consists of the formation of a myelin sheath around a nerve fiber, enabling the effective transmission of neural impulses. As the brain undergoes myelination, there is a subsequent change in the contrast between gray matter and white matter as observed in MR scans. In this work, gray-white matter contrast is proposed as an effective measure of appearance which is relatively invariant to location, scanner type, and scanning conditions. To validate this, contrast is computed over various cortical regions for an adult human phantom. MR (Magnetic Resonance) images of the phantom were repeatedly generated using different scanners, and at different locations. Contrast displays less variability over changing conditions of scan compared to intensity-based measures, demonstrating that it is less dependent than intensity on external factors. Additionally, contrast is used to analyze longitudinal MR scans of the early brain, belonging to healthy controls and Down's Syndrome (DS) patients. Kernel regression is used to model subject-specific trajectories of contrast changing with time. Trajectories of contrast changing with time, as well as time-based biomarkers extracted from contrast modeling, show large differences between groups. The preliminary applications of contrast based analysis indicate its future potential to reveal new information not covered by conventional volumetric or deformation-based analysis, particularly for distinguishing between normal and abnormal growth patterns.

  16. Growth and characterization of ZnSe nanoparticles

    SciTech Connect

    Sharma, Shail Malik, Mukhtar Ah. Chandel, Tarun Thakur, Vikas Rajaram, P.

    2014-04-24

    ZnSe nanoparticles were prepared using a chemical bath deposition technique. X-ray diffraction study shows that the ZnSe crystallizes in the cubic phase. The crystallite size of the ZnSe samples calculated using the Scherrer’s formula was found to be slightly smaller than the Bohr exciton radius of bulk ZnSe. SEM studies show the growth of a mixture of nanorods and spherical nanoparticles. EDAX analysis confirms that the synthesized ZnSe nanoparticles are of good stiochiometry. Optical studies show the blue shift in the absorption edge for ZnSe nanoparticles caused by quantum confinement.

  17. Growth and Characterization of Silicon at the 2D Limit

    NASA Astrophysics Data System (ADS)

    Mannix, Andrew; Kiraly, Brian; Hersam, Mark; Guisinger, Nathan

    2015-03-01

    Because bulk silicon has dominated the development of microelectronics over the past 50 years, the recent interest in two-dimensional (2D) materials (e.g., graphene, MoS2, phosphorene, etc.) naturally raises questions regarding the growth and properties of silicon at the 2D limit. Utilizing atomic-scale, ultra-high vacuum (UHV) scanning tunneling microscopy (STM), we have investigated the 2D limits of silicon growth on Ag(111). In agreement with previous reports of sp2-bonded silicene phases, we observe the temperature-dependent evolution of ordered 2D phases. However, we attribute these to apparent Ag-Si surface alloys. At sufficiently high silicon coverage, we observe the precipitation of crystalline, sp3-bonded Si(111) domains. These domains are capped with a √3 honeycomb phase that is indistinguishable from the silver-induced √3 honeycomb-chained-trimer reconstruction on bulk Si(111). Further ex-situcharacterization with Raman spectroscopy, atomic force microscopy, cross-sectional transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy reveals that these sheets are ultrathin sheets of bulk-like, (111) oriented, sp3 silicon. Even at the 2D limit, scanning tunneling spectroscopy shows that these silicon nanosheets exhibit semiconducting electronic characteristics.

  18. Growth and characterization of epitaxial silver indium diselenide

    NASA Astrophysics Data System (ADS)

    Pena Martin, Pamela

    Photovoltaics (solar cells) are a key player in the renewable energy frontier, and will become increasingly important as their cost per watt continues to drop, especially if fossil fuel costs increase. One particularly promising photovoltaic technology is based on chalcopyrite-structure semiconductors. Within the chalcopyrite compounds the highest efficiency thin film solar cell absorber material to date is Cu(In,Ga)Se2 (CIGS). While current efficiency records are over 21% for single-junction cells, there is still room for improvement. Replacing some of the Cu with Ag has been shown to be beneficial in CIGS devices. However, the Ag- containing chalcopyrites are still relatively unknown in terms of their growth mechanism, energetics, and surface atomic and electronic properties. These are best inferred through study of epitaxial films, yet they have little mention in literature and have not been the subject of a detailed study. This work describes the growth of epitaxial AgInSe2 (AIS) on GaAs substrates, studying the morphology, structure, and surface properties to understand how growth takes place. It also seeks to experimentally determine the surface electronic and atomic structure at the atomic scale to gain insight into the part of the material that forms the heterojunction that collects photon energy in the device. Finally, this work seeks to compare and contrast these findings with what is known about CIGS to determine where similarities and, more importantly, the differences may lie. This study has found that single phase tetragonal AIS can be epitaxially grown on GaAs, as illustrated by x-ray diffraction (XRD), transmission electron microscope (TEM), and surface morphology data. Like CIGS, the close packed polar (112) planes have the lowest energy. The morphology points to a difference in step dynamics, leading to less faceted, straight edged island shapes compared to CIGS. Epitaxial temperature as a function of growth direction shows a different trend in

  19. Characterization of reproduction and growth of American robins at the Fernald Environmental Management Project, 1991

    SciTech Connect

    Osborne, D.R.; Ambrose, D.M.; Simpson, J.C. )

    1992-11-01

    As part of a Biological and Ecological Site Characterization of the Fernald Environmental Management Project (FEMP), suppressed growth in onsite American robin nestlings was discovered in 1987 and in 1990. However, the causal factors relating to suppressed growth were not investigated. This study was initiated to determine if growth suppression still existed, and if so, the possible relationship of FEMP land management practices and soil contaminants through food chains to growth and reproductive fitness. This study was expanded to include five offsite sampling sites, as well as analyses of soils and earthworms for uranium, pesticides/herbicides, and heavy metals.

  20. MOCVD manifold switching effects on growth and characterization

    NASA Astrophysics Data System (ADS)

    Clark, Ivan O.; Fripp, Archibald L.; Jesser, William A.

    1991-02-01

    A combined modeling and experimental approach is used to quantify the effects of various manifold components on the switching speed in metalorganic chemical vapor deposition (MOCVD). In particular, two alternative vent-run high-speed switching manifold designs suitable for either continuous or interrupted growth have been investigated. Both designs are incorporated in a common manifold, instrumented with a mass spectrometer. The experiments have been performed using nitrogen as the transport gas and argon as the simulated source gas. The advantages and limitations of two designs are discussed. It is found that while constant flow manifold switching systems may have fluid dynamic advantages, care must be taken to minimize sections of the supply manifold with low flow rates if rapid changes in alloy composition are required.

  1. Growth and characterization of YAG:Cr4+epitaxial films

    NASA Astrophysics Data System (ADS)

    Ubizskii, Sergii B.; Syvorotka, Igor M.; Melnyk, Sergii S.; Matkovskii, Andrej O.; Kopczynski, Krzysztof; Mierczyk, Zygmunt; Frukacz, Zygmunt

    1999-03-01

    Epitaxial films with thickness of 10 - 250 micrometers of yttrium aluminum garnet (YAG) doped with Cr were grown by liquid phase epitaxy technique on YAG:Nd substrates. Co-doping with Mg2+ is used to force the Cr4+ valent state formation. Dependence of absorption spectra of obtained films on melt-solution composition, growth conditions and thermal treatment in reducing and oxidizing atmospheres is studied. A very intensive absorption band in UV region with maximum at 275 nm was found both in co-doped and YAG:Mg2+ epifilms caused probably by oxygen vacancies compensating the excess charge of Mg2+. Its intensity correlates with Cr4+ content in the film in that way: it decreases with Cr4+ entering in the film. The absorption being characteristic for YAG:Cr4+ crystals is found in co-doped films grown at higher temperatures (1000 - 1100 degree(s)C). The processes occurring during annealing are discussed.

  2. Rubber Characterization with Fatigue and Crack Growth Analysis

    NASA Astrophysics Data System (ADS)

    Perier, Laurent; Favier, Arnaud

    2010-06-01

    Dynamic Mechanical Analysis brings advanced capabilities to generate quantitative dynamic property data of rubber compounds for modelers and end users. Additionally to the recognized DMA testing benefits, a new METRAVIB Analyzer DMA+300 includes new testing solutions for analyzing rubbers mechanical property data under extended testing conditions closer to the real product's life conditions. The DMA+300 is specifically designed and dimensioned for fatigue tests on elastomers and crack growth tests. Combined with new MULTITEST software, DMA+300 makes possible to generate multi harmonics excitation and to control the application of a specific wave form to the specimen of rubber. This paper presents the main benefits available with this machine in the domain of rubber and elastomer applications.

  3. Growth and characterization of CNT–TiO2 heterostructures

    PubMed Central

    Utke, Ivo; Michler, Johann; Ilari, Gabriele; Rossell, Marta D; Erni, Rolf

    2014-01-01

    Summary A thriving field in nanotechnology is to develop synergetic functions of nanomaterials by taking full advantages of unique properties of each component. In this context, combining TiO2 nanocrystals and carbon nanotubes (CNTs) offers enhanced photosensitivity and improved photocatalytic efficiency, which is key to achieving sustainable energy and preventing environmental pollution. Hence, it has aroused a tremendous research interest. This report surveys recent research on the topic of synthesis and characterization of the CNT–TiO2 interface. In particular, atomic layer deposition (ALD) offers a good control of the size, crystallinity and morphology of TiO2 on CNTs. Analytical transmission electron microscopy (TEM) techniques such as electron energy loss spectroscopy (EELS) in scanning transmission mode provides structural, chemical and electronic information with an unprecedented spatial resolution and increasingly superior energy resolution, and hence is a necessary tool to characterize the CNT–TiO2 interface, as well as other technologically relevant CNT–metal/metal oxide material systems. PMID:25161830

  4. Growth and characterizations of semipolar (1122) InN

    SciTech Connect

    Dinh, Duc V.; Skuridina, D.; Solopow, S.; Frentrup, M.; Pristovsek, M.; Vogt, P.; Kneissl, M.; Ivaldi, F.; Kret, S.; Szczepanska, A.

    2012-07-01

    We report on metal-organic vapor phase epitaxial growth of (1122) InN on (1122) GaN templates on m-plane (1010) sapphire substrates. The in-plane relationship of the (1122) InN samples is [1123]{sub InN} Double-Vertical-Line Double-Vertical-Line [0001]{sub sapphire} and [1100]{sub InN} Double-Vertical-Line Double-Vertical-Line [1210]{sub sapphire}, replicating the in-plane relationship of the (1122) GaN templates. The surface of the (1122) InN samples and the (1122) GaN templates shows an undulation along [1100]{sub InN,GaN}, which is attributed to anisotropic diffusion of indium/gallium atoms on the (1122) surfaces. The growth rate of the (1122) InN layers was 3-4 times lower compared to c-plane (0001) InN. High resolution transmission electron microscopy showed a relaxed interface between the (1122) InN layers and the (1122) GaN templates, consistent with x-ray diffraction results. Basal plane stacking faults were found in the (1122) GaN templates but they were terminated at the InN/(1122) GaN interface due to the presence of misfit dislocations along the entire InN/GaN interface. The misfit dislocations were contributed to the fully relaxation and the tilts of the (1122) InN layers. X-ray photoelectron spectroscopy was used to determine the polarity of the grown (1122) InN sample, indicating an In-polar (1122) InN. The valence band maximum was determined to be at (1.7 {+-} 0.1) eV for the (1122) InN sample, comparable to In-polar c-plane InN.

  5. Vapour growth and characterization of beta indium sesquitelluride crystals

    NASA Astrophysics Data System (ADS)

    Reshmi, P. M.; Kunjomana, A. G.; Chandrasekharan, K. A.; Teena, M.

    2014-05-01

    Physical Vapour Deposition (PVD) provides stoichiometric crystals of different morphology, depending upon the materials, geometry of ampoules, temperature profiles, growth parameters and kinetics of crystallization. The crystal forms such as needles, platelets and spherulites of beta indium sesquitelluride (β-In2Te3) were produced by controlling the temperature of source and growth zones. The X-Ray Diffraction (XRD) and chemical analysis of the spherulitic crystals confirmed zinc blende structure with beta phase. Their resistivity (135.16 Ω cm) at room temperature (300 K) was determined by van der Pauw method. The temperature dependence of DC conductivity was investigated using the conventional two-probe technique. The variation of dielectric constant (ε1) and dielectric loss (tan δ) with temperature has been studied for different frequencies (1 kHz-1 MHz). The AC conductivity, σac(ω) was found to vary with angular frequency as ωs, where s is the frequency exponent. The values of s lie very close to unity and show a slight decrease with increase in temperature, which indicate a Correlated Barrier Hopping (CBH) between centres forming Intimate Valence Alternation Pairs (IVAP). The activation energy for conduction ranges from 0.187 eV to 0.095 eV. The microhardness of β-In2Te3 spherulites is found to be 353.5 kg/mm2, which is higher than that of other semiconducting chalcogenides. The results thus obtained on crystals grown from vapour phase open up ample possibilities for radiation detector applications.

  6. Characterization of Tack Strength Based on Cavity-Growth Criterion.

    PubMed

    Takahashi, Kosuke; Yamagata, Yuichiro; Inaba, Kazuaki; Kishimoto, Kikuo; Tomioka, Shiori; Sugizaki, Toshio

    2016-04-12

    The adhesive force generated by a small short-term pressure, called tack, is measured by a probe tack test on pressure-sensitive adhesives (PSAs); the maximum force is evaluated by cavity growth at the interface between the PSA layer and the probe surface. As the PSA layer becomes thinner, it is more difficult to measure the tack with a cylindrical probe because of the uneven contact resulting from misalignment. A spherical probe is preferable to obtain reproducible contact on the PSA layer, but the contact area should be taken into account if the contact pressure affects the tack performance. Tack was measured on PSAs with various thicknesses in different contact areas to clarify their effect. The results showed that a larger contact area on a thinner PSA generated higher adhesive stress with larger strain. It was found that the maximum adhesive stress was not affected by the contact pressure, but it was strongly correlated to the contact radius divided by the PSA thickness. In addition, a video microscope observation showed that, in all of the experimental cases, the adhesive stress always reached the maximum when cavities were generated at the interface between the PSA and probe surface. Therefore, the criterion of cavity growth was introduced for the evaluation of the maximum adhesive stress. As a result, the experimental results, even at different release rates, were in good agreement with the estimation by considering the effect of confining a thin layer. Furthermore, the theoretical estimation indicated the ultimate value, which was not dependent upon the PSA thickness or contact area. It was defined as a material property, referred to as the "ultimate tack strength" of PSAs. PMID:26991212

  7. Anomalous transport regimes and asymptotic concentration distributions in the presence of advection and diffusion on a comb structure

    NASA Astrophysics Data System (ADS)

    Dvoretskaya, Olga A.; Kondratenko, Peter S.

    2009-04-01

    We study the transport of impurity particles on a comb structure in the presence of advection. The main body concentration and asymptotic concentration distributions are obtained. Seven different transport regimes occur on the comb structure with finite teeth: classical diffusion, advection, quasidiffusion, subdiffusion, slow classical diffusion, and two kinds of slow advection. Quasidiffusion deserves special attention. It is characterized by a linear growth of the mean-square displacement. However, quasidiffusion is an anomalous transport regime. We established that a change in transport regimes in time leads to a change in regimes in space. Concentration tails have a cascade structure, namely, consisting of several parts.

  8. Growth and characterization of thiosemicarbazide hydrochloride: A semiorganic NLO material

    NASA Astrophysics Data System (ADS)

    Santhakumari, R.; Ramamurthi, K.; Babu, R. Ramesh; Evans, Helen Stoeckli; Bhagavannarayana, G.; Hema, R.

    2011-11-01

    Thiosemicarbazide hydrochloride (TSCHCL) was synthesized by mixing thiosemicarbazide and hydrochloride in 1:1 molar ratio in double distilled water. Single crystals of TSCHCL were grown by slow evaporation at room temperature and were characterized by single crystal X-ray diffraction study to determine the molecular structure and by FT-IR, 1H and 13C NMR spectral analyses to confirm the synthesized compound. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. The transmission spectrum of TSCHCL showed that the crystal is transparent in the wavelength range 380-1100 nm. High resolution X-ray diffractometry (HRXRD) was employed to evaluate the perfection of the grown crystal. Mechanical properties of the grown crystal were studied using Vickers microhardness test. Second harmonic generation efficiency of the powdered TSCHCL was tested using Nd:YAG laser and is ˜1.5 times that of potassium dihydrogen orthophosphate.

  9. Perovskite Oxide Thin Film Growth, Characterization, and Stability

    NASA Astrophysics Data System (ADS)

    Izumi, Andrew

    Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough

  10. Topological characterization of the transition from laminar regime to fully developed turbulence in the resistive pressure-gradient-driven turbulence model

    SciTech Connect

    Garcia, L.; Carreras, B. A.; Llerena, I.; Calvo, I.

    2009-10-15

    For the resistive pressure-gradient-driven turbulence model, the transition from laminar regime to fully developed turbulence is not simple and goes through several phases. For low values of the plasma parameter {beta}, a single quasicoherent structure forms. As {beta} increases, several of these structures may emerge and in turn take the dominant role. Finally, at high {beta}, fully developed turbulence with a broad spectrum is established. A suitable characterization of this transition can be given in terms of topological properties of the flow. Here, we analyze these properties that provide an understanding of the turbulence-induced transport and give a measure of the breaking of the homogeneity of the turbulence. To this end, an approach is developed that allows discriminating between topological properties of plasma turbulence flows that are relevant to the transport dynamics and the ones that are not. This is done using computational homology tools and leads to a faster convergence of numerical results for a fixed level of resolution than previously presented in Phys. Rev. E 78, 066402 (2008)

  11. Single crystal growth and characterization of holmium tartrate trihydrate

    NASA Astrophysics Data System (ADS)

    Want, Basharat; Ahmad, Farooq; Kotru, P. N.

    2007-02-01

    The growth of holmium tartrate trihydrate (HTT) single crystals is achieved in organic (agar-agar) as well as in inorganic (silica) gels by single gel diffusion method. Results of the study on nucleation kinetics of crystals grown in silica gel are described. The crystals exhibit the morphological form of a tetragonal dipyramidal class with {0 0 1} and {1 1 1} as dominant faces. Elemental and thermogravimetric analysis (TGA) supplemented by energy dispersive analysis of X-rays (EDAX) support the suggested chemical formula of the grown crystals to be [Ho (C 4H 4O 6) (C 4H 5O 6)·3H 2O]. Single crystal X-ray diffraction (XRD) studies indicate that the crystals belong to tetragonal system with the cell parameters a=5.97 Å, c=36.09 Å, bearing the space group P4 1. Fourier transform infrared (FT-IR) spectroscopic study indicates the presence of tartrate ligands and suggests that one of the tartrate ions is singly ionized. TGA suggests that the material is thermally stable up to 220 °C.

  12. Functional Characterization of Pseudomonas Contact Dependent Growth Inhibition (CDI) Systems

    PubMed Central

    Mercy, Chryslène; Ize, Bérengère; Salcedo, Suzana P.; de Bentzmann, Sophie; Bigot, Sarah

    2016-01-01

    Contact-dependent inhibition (CDI) toxins, delivered into the cytoplasm of target bacterial cells, confer to host strain a significant competitive advantage. Upon cell contact, the toxic C-terminal region of surface-exposed CdiA protein (CdiA-CT) inhibits the growth of CDI- bacteria. CDI+ cells express a specific immunity protein, CdiI, which protects from autoinhibition by blocking the activity of cognate CdiA-CT. CdiA-CT are separated from the rest of the protein by conserved peptide motifs falling into two distinct classes, the “E. coli”- and “Burkholderia-type”. CDI systems have been described in numerous species except in Pseudomonadaceae. In this study, we identified functional toxin/immunity genes linked to CDI systems in the Pseudomonas genus, which extend beyond the conventional CDI classes by the variability of the peptide motif that delimits the polymorphic CdiA-CT domain. Using P. aeruginosa PAO1 as a model, we identified the translational repressor RsmA as a negative regulator of CDI systems. Our data further suggest that under conditions of expression, P. aeruginosa CDI systems are implicated in adhesion and biofilm formation and provide an advantage in competition assays. All together our data imply that CDI systems could play an important role in niche adaptation of Pseudomonadaceae. PMID:26808644

  13. Growth and characterization of chalcone derivative single crystal

    NASA Astrophysics Data System (ADS)

    Ravindrachary, V.; Crasta, Vincent; Bhajantri, R. F.; Poojari, Boja

    2005-02-01

    A novel organic non-linear optical material 1-(4-methylphenyl)-3-(4- N, N dimethyl amino phenyl)-2-propen-1-one has been synthesized by the standard method. The synthesized compound was purified by repeated re-crystallization process. To confirm the synthesized compound an FT-IR spectra was recorded and the various functional groups present in the compound were identified. Good quality crystals were grown by slow evaporation technique using acetone as solvent. The grown crystals were characterized by UV-Visible and powder X-ray diffraction (XRD) studies. The XRD study, revealed that the crystals are in the orthorhombic system with a space group P2 12 12 1 and the corresponding lattice parameters are a=7.3710 Å, b=11.6200 Å and c=17.6590 Å. Using optical spectra, the optical energy gap of the crystal is estimated to be 2.40 eV. The refractive index of the crystal is measured using Brewster's angle method and the density using standard method. The second harmonic generation (SHG) efficiency of 0.8 times that of Urea of the crystal was obtained using ND-YAG laser ( λ=1064 nm).

  14. Growth and characterization of RFe_6Ge6 single crystals

    NASA Astrophysics Data System (ADS)

    Avila, M. A.; Bud'Ko, S. L.; Canfield, P. C.

    2003-03-01

    The RFe_6Ge6 family of magnetic compounds is formed by the positioning of a rare earth element (and a few other metals) in between Fe planes of the parent FeGe structure. The Fe ions are reported to order ferromagnetically within each plane, but anti-ferromagnetically between neighboring planes. Thus, there is a cancellation of the net magnetic field due to Fe at the rare earth site and the compounds display independent ordering of the Fe and R sublattices, the former occurring above 400 K and the latter occurring well below 100 K (Ryan and Cadogan, J. Appl. Phys. 79 (1996) 6004). We have successfully obtained the first flux-grown single crystals for several members of this family, which allow for a better understanding of the anisotropic ground state and other properties of this series. Characterizations by X-Ray diffraction, temperature and field dependent magnetization, specific heat and resistivity will be presented and discussed. We acknowledge the help of R. A. Ribeiro and C. Petrovic in the X-Ray measurements. Ames Laboratory is operated for the US Department of Energy by Iowa State University under Contract No. W-7405-Eng-82. This work was supported by the Director for Energy Research, Office of Basic Energy Sciences.

  15. Growth, characterization, modeling and device applications of semiconductor nanowire networks

    NASA Astrophysics Data System (ADS)

    Lohn, Andrew J.

    Semiconducting nanowire networks composed specifically of indium phosphide or silicon are developed with the goal of understanding their electrical, thermal and optoelectronic properties while developing scalable, manufacturable solutions to a number of problems of contemporary interest to society, with particular emphasis on direct conversion of heat to electricity. Nanowire networks are grown by metal organic chemical vapor deposition on non-single crystalline surfaces leading to highly interconnected networks of nanowires capable of long-range three-dimensional transport while retaining many of the unique properties of highly conned nanowire structures and displaying advantageous and unique properties such as mechanical flexibility. Growth of semiconducting nanowire networks is discussed in depth, especially relating to the role of the non-single crystalline surfaces from which they grow and morphological changes associated with doping. Finite element simulations suggest that the physical intersections present within a nanowire network are found to play a complex and potentially useful role in thermal transport and in electrical transport through experiment, demonstrating quantized conductance for the first time at room temperature. Electrical transport over distances far in excess of the dimensions of the individual nanowires is also studied experimentally by applying surface photovoltage techniques for the first time to nanowire networks. The theoretical model developed to analyze data from this, first of its type, experiment reveals insights that can aid in developing improved thermoelectric devices. Such thermoelectric devices were fabricated using a highly scalable and very low cost approach. Thermoelectric testing displays large series electrical resistance but Seebeck voltages comparable to its bulk counterpart. The preliminary results clearly indicate that if series electrical resistance can be decreased, nanowire networks will be an excellent candidate

  16. Thermodynamic characterization of an intermediate state of human growth hormone.

    PubMed Central

    Gomez-Orellana, I.; Variano, B.; Miura-Fraboni, J.; Milstein, S.; Paton, D. R.

    1998-01-01

    The thermal denaturation of recombinant human growth hormone (rhGH) was studied by differential scanning calorimetry and circular dichroism spectroscopy (CD). The thermal unfolding is reversible only below pH 3.5, and under these conditions a single two-state transition was observed between 0 and 100 degrees C. The magnitudes of the deltaH and deltaCp of this transition indicate that it corresponds to a partial unfolding of rhGH. This is also supported by CD data, which show that significant secondary structure remains after the unfolding. Above pH 3.5 the thermal denaturation is irreversible due to the aggregation of rhGH upon unfolding. This aggregation is prevented in aqueous solutions of alcohols such as n-propanol, 2-propanol, or 1,2-propanediol (propylene glycol), which suggests that the self-association of rhGH is caused by hydrophobic interactions. In addition, it was found that the native state of rhGH is stable in relatively high concentrations of propylene glycol (up to 45% v/v at pH 7-8 or 30% at pH 3) and that under these conditions the thermal unfolding is cooperative and corresponds to a transition from the native state to a partially folded state, as observed at acidic pH in the absence of alcohols. In higher concentrations of propylene glycol, the tertiary structure of rhGH is disrupted and the cooperativity of the unfolding decreases. Moreover, the CD and DSC data indicate that a partially folded intermediate with essentially native secondary structure and disordered tertiary structure becomes significantly populated in 70-80% propylene glycol. PMID:9655339

  17. The growth and in situ characterization of chemical vapor deposited SiO2

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Chang, R. R.; Lile, D. L.

    1987-01-01

    This paper reports the results of studies of the kinetics of remote (indirect) plasma enhanced low pressure CVD growth of SiO2 on Si and InP and of the in situ characterization of the electrical surface properties of InP during CVD processing. In the latter case photoluminescence was employed as a convenient and sensitive noninvasive method for characterizing surface trap densities. It was determined that, provided certain precautions are taken, the growth of SiO2 occurs in a reproducible and systematic fashion that can be expressed in an analytic form useful for growth rate prediction. Moreover, the in situ photoluminescence studies have yielded information on sample degradation resulting from heating and chemical exposure during the CVD growth.

  18. Growth and characterization of nanocrystalline zirconium nitride-inconel structures

    NASA Astrophysics Data System (ADS)

    Aouadi, S. M.; Maeruf, T.; Sodergren, M.; Mihut, D. M.; Rohde, S. L.; Xu, J.; Mishra, S. R.

    2005-07-01

    This paper reports on the investigation of the physical, chemical, optical, mechanical, and tribological properties of reactively sputtered zirconium nitride-inconel composite nanocrystalline mixture films. These films were co-sputtered from a Zr and an inconel targets onto Si (111) substrates at room temperature using a fixed power to the Zr target (PZr) and a fixed flow of nitrogen and argon. Two sets of samples were produced by (1) varying the power to the inconel target (Pinc) and using a fixed bias voltage Vb and (2) by varying Vb and keeping Pinc fixed. The elemental composition was deduced from x-ray photoelectron spectroscopy, and was found to be influenced by Pinc and Vb. X-ray diffraction revealed the presence of nanocrystals of ZrN with a pattern typical of the NaCl structure. The grain size was found to decrease with the increase in ``inconel'' content in the film. The optical constants were measured using spectroscopic ellipsometry and were subsequently simulated using a Drude-Lorentz model. A correlation between film structure-composition and optical constants was established. The hardness and elastic modulus of each sample were measured by nanoindentation. The hardest films were produced using a Vb=-130 V bias voltage and Pinc=4 W. Microwear measurements were carried out using positive constant normal loads and the wear tracks were imaged and processed. The measured values for the friction coefficients, residual depth of tip indentations, wear volumes, and surface roughness were reported. The lowest recorded wear volume using a load of 4 mN was 10-3 μm. Finally, the coatings were worn against ball-bearing steel using a ball-on-disk tribotester. Characterization of the wear tracks were performed by profilometry. A low wear coefficient of 1.7×10-7 mm3/s was obtained for a load of 5 N.

  19. Growth and characterization of silicon-based optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Filios, Adam A.

    layers sandwiched between monolayers of oxygen. The key for its fabrication is that epitaxial growth of silicon may be continued beyond the interruption with exposure to oxygen. Prepared by an Ultra High Vacuum (UHV), Molecular Beam Epitaxial (MBE) technique, the multilayer device is extremely stable and robust, and can be readily integrated with conventional silicon VLSI processing. In addition, it exhibits bright, room temperature, visible photoluminescent and electroluminescent emission, at least as strong as that of porous silicon. With its efficient light emission, robustness and stability, the c-Si/O superlattice may hold the promise of a truly integrated silicon-based optoelectronic device.

  20. Unidirectional growth of benzil crystal from solution by Sankaranarayanan-Ramasamy method and its characterization.

    PubMed

    Rajalakshmi, M; Shyju, T S; Indirajith, R; Gopalakrishnan, R

    2012-02-01

    Good quality <100> benzil single crystal with a diameter 18 mm and length 75 mm was successfully grown from solution by the unidirectional growth method of Sankaranarayanan-Ramasamy (SR) for the first time in the literature. The seed crystals have been harvested from conventional solution growth technique and subsequently used for unidirectional growth. The grown crystal was subjected to various characterization studies. The results of UV-vis spectral analysis, photoluminescence, etching and microhardness studies were compared with conventional solution grown crystal to that of SR method grown crystal. The quality of SR method grown benzil crystal is better than conventional solution grown crystal. PMID:22088560

  1. Unidirectional growth of benzil crystal from solution by Sankaranarayanan-Ramasamy method and its characterization

    NASA Astrophysics Data System (ADS)

    Rajalakshmi, M.; Shyju, T. S.; Indirajith, R.; Gopalakrishnan, R.

    2012-02-01

    Good quality <1 0 0> benzil single crystal with a diameter 18 mm and length 75 mm was successfully grown from solution by the unidirectional growth method of Sankaranarayanan-Ramasamy (SR) for the first time in the literature. The seed crystals have been harvested from conventional solution growth technique and subsequently used for unidirectional growth. The grown crystal was subjected to various characterization studies. The results of UV-vis spectral analysis, photoluminescence, etching and microhardness studies were compared with conventional solution grown crystal to that of SR method grown crystal. The quality of SR method grown benzil crystal is better than conventional solution grown crystal.

  2. Characterizing tropical tree species growth strategies: learning from inter-individual variability and scale invariance.

    PubMed

    Le Bec, Jimmy; Courbaud, Benoit; Le Moguédec, Gilles; Pélissier, Raphaël

    2015-01-01

    Understanding how tropical tree species differ in their growth strategies is critical to predict forest dynamics and assess species coexistence. Although tree growth is highly variable in tropical forests, species maximum growth is often considered as a major axis synthesizing species strategies, with fast-growing pioneer and slow-growing shade tolerant species as emblematic representatives. We used a hierarchical linear mixed model and 21-years long tree diameter increment series in a monsoon forest of the Western Ghats, India, to characterize species growth strategies and question whether maximum growth summarizes these strategies. We quantified both species responses to biotic and abiotic factors and individual tree effects unexplained by these factors. Growth responses to competition and tree size appeared highly variable among species which led to reversals in performance ranking along those two gradients. However, species-specific responses largely overlapped due to large unexplained variability resulting mostly from inter-individual growth differences consistent over time. On average one-third of the variability captured by our model was explained by covariates. This emphasizes the high dimensionality of the tree growth process, i.e. the fact that trees differ in many dimensions (genetics, life history) influencing their growth response to environmental gradients, some being unmeasured or unmeasurable. In addition, intraspecific variability increased as a power function of species maximum growth partly as a result of higher absolute responses of fast-growing species to competition and tree size. However, covariates explained on average the same proportion of intraspecific variability for slow- and fast-growing species, which showed the same range of relative responses to competition and tree size. These results reflect a scale invariance of the growth process, underlining that slow- and fast-growing species exhibit the same range of growth strategies. PMID

  3. Characterizing Tropical Tree Species Growth Strategies: Learning from Inter-Individual Variability and Scale Invariance

    PubMed Central

    Le Bec, Jimmy; Courbaud, Benoit; Le Moguédec, Gilles; Pélissier, Raphaël

    2015-01-01

    Understanding how tropical tree species differ in their growth strategies is critical to predict forest dynamics and assess species coexistence. Although tree growth is highly variable in tropical forests, species maximum growth is often considered as a major axis synthesizing species strategies, with fast-growing pioneer and slow-growing shade tolerant species as emblematic representatives. We used a hierarchical linear mixed model and 21-years long tree diameter increment series in a monsoon forest of the Western Ghats, India, to characterize species growth strategies and question whether maximum growth summarizes these strategies. We quantified both species responses to biotic and abiotic factors and individual tree effects unexplained by these factors. Growth responses to competition and tree size appeared highly variable among species which led to reversals in performance ranking along those two gradients. However, species-specific responses largely overlapped due to large unexplained variability resulting mostly from inter-individual growth differences consistent over time. On average one-third of the variability captured by our model was explained by covariates. This emphasizes the high dimensionality of the tree growth process, i.e. the fact that trees differ in many dimensions (genetics, life history) influencing their growth response to environmental gradients, some being unmeasured or unmeasurable. In addition, intraspecific variability increased as a power function of species maximum growth partly as a result of higher absolute responses of fast-growing species to competition and tree size. However, covariates explained on average the same proportion of intraspecific variability for slow- and fast-growing species, which showed the same range of relative responses to competition and tree size. These results reflect a scale invariance of the growth process, underlining that slow- and fast-growing species exhibit the same range of growth strategies. PMID

  4. Characterizing Submonolayer Growth of 6P on Mica: Capture Zone Distributions vs. Growth Exponents and the Role of Hot Precursors

    NASA Astrophysics Data System (ADS)

    Einstein, T. L.; Morales-Cifuentes, Josue; Pimpinelli, Alberto

    2015-03-01

    Analyzing capture-zone distributions (CZD) using the generalized Wigner distribution (GWD) has proved a powerful way to access the critical nucleus size i. Of the several systems to which the GWD has been applied, we consider 6P on mica, for which Winkler's group found i ~ 3 . Subsequently they measured the growth exponent α (island density ~Fα , for flux F) of this system and found good scaling but different values at small and large F, which they attributed to DLA and ALA dynamics, but with larger values of i than found from the CZD analysis. We investigate this result in some detail. The third talk of this group describes a new universal relation between α and the characteristic exponent β of the GWD. The second talk reports the results of a proposed model that takes long-known transient ballistic adsorption into account, for the first time in a quantitative way. We find several intermediate scaling regimes, with distinctive values of α and an effective activation energy. One of these, rather than ALA, gives the best fit of the experimental data and a value of i consistent with the CZD analysis. Work at UMD supported by NSF CHE 13-05892.

  5. Photophysical Analysis of the Formation of Organic–Inorganic Trihalide Perovskite Films: Identification and Characterization of Crystal Nucleation and Growth

    PubMed Central

    2016-01-01

    In this work we demonstrate that the different processes occurring during hybrid organic–inorganic lead iodide perovskite film formation can be identified and analyzed by a combined in situ analysis of their photophysical and structural properties. Our observations indicate that this approach permits unambiguously identifying the crystal nucleation and growth regimes that lead to the final material having a cubic crystallographic phase, which stabilizes to the well-known tetragonal phase upon cooling to room temperature. Strong correlation between the dynamic and static photoemission results and the temperature-dependent X-ray diffraction data allows us to provide a description and to establish an approximate time scale for each one of the stages and their evolution. The combined characterization approach herein explored yields key information about the kinetics of the process, such as the link between the evolution of the defect density during film formation, revealed by a fluctuating photoluminescence quantum yield, and the gradual changes observed in the PbI2-related precursor structure. PMID:26949439

  6. Crystal growth and characterization of CdInGaS 4 and related compounds

    NASA Astrophysics Data System (ADS)

    Endo, Saburo; Ando, Shizutoshi; Matsushita, Hiroaki; Nomura, Shigetaka; Irie, Taizo; Nakanishi, Hisayuki; Noda, Yasutoshi; Takizawa, Takeo; Toyoda, Taro

    1990-01-01

    Crystal growth of CdInGaS 4 was performed by normal freezing and Bridgman methods. The characterization of the crystals was done along the growth direction by X-ray diffraction, optical absorption, photoluminescence, compositional analysis and etch pit observation. The physical properties investigated are essentially constant along the growth direction and independent of the method of crystal growth. The X-ray powder diffraction pattern of CdInGaS 4 can roughly be reproduced by a computer simulation based on the structure deduced from that of ZnIn 2S 4. The crystal structure of Cd 3InGaS 6 was found to be a laminated structure composed of CdInGaS 4 and Cds.

  7. Growth and characterization of Cu2ZnSnS4 nanostructures using anodized aluminum as the growth mask

    NASA Astrophysics Data System (ADS)

    Chan, C. P.; Chen, Z.; Lam, H.; Surya, C.

    2009-08-01

    In this paper we report the growth and characterization of Cu2ZnSnS4 (CZTS) nanostructures by co-electrodeposition technique using CuCl2, SnCl2 and ZnCl2 as sources and choline-based ionic liquid (IL) as the electrolyte. X-ray diffraction analysis of CZTS thin films grown by this technique indicated that the films have a kesterite structure with preferred grain orientation along (112). It is found that the energy bandgap of the material is about 1.49eV and the optical absorption coefficient is in the order of 104cm-1. Anodized aluminum oxide (AAO) was used as the growth mask for the growth of the nanostructures. Anodization of the aluminum foil was carried out in phosphoric acid solution at 1°C and a potential of 40 to 100V was applied. Sulfurization of the rods was performed in elemental sulfur vapor at 450°C for four hours using N2 as the ambient gas. Experimental results show that nanotubes were formed using the technique and the diameter can be well controlled by varying the applied potential in the anodization process. Electron diffraction experiments show that a mixture of single- and poly-crystalline nanostructures was found.

  8. Hydrotechnical facilities within the Chernobyl nuclear power plant exclusion zone: impacts on hydrologic regime and plant growth patterns of floodplain water bodies of the Pripyat River.

    PubMed

    Gudkov, D I; Zub, L N; Savitsky, A L

    2003-01-01

    As result of the Chernobyl nuclear power plant accident the territory of the left-bank flood-lands of the Pripyat River have undergone intensive radionuclide contamination. With the purpose of preventing the washing away of radioactive substances, a complex of flood protection dams was constructed. This construction changed the hydrological regime of these territories and caused overgrowth by higher aquatic plants. Absence of a flowing mode of reservoirs, the stagnant phenomena during spring and seasonal high waters on the embank site have caused amplification of eutrophication processes, swamping and, connected with it, increase of water-marsh floristic complex in the structure of the vegetative cover. PMID:14653638

  9. Isolation and characterization of plant growth-promoting rhizobacteria from wheat rhizosphere and their effect on plant growth promotion.

    PubMed

    Majeed, Afshan; Abbasi, M Kaleem; Hameed, Sohail; Imran, Asma; Rahim, Nasir

    2015-01-01

    The present study was conducted to characterize the native plant growth promoting (PGP) bacteria from wheat rhizosphere and root-endosphere in the Himalayan region of Rawalakot, Azad Jammu and Kashmir (AJK), Pakistan. Nine bacterial isolates were purified, screened in vitro for PGP characteristics and evaluated for their beneficial effects on the early growth of wheat (Triticum aestivum L.). Among nine bacterial isolates, seven were able to produce indole-3- acetic acid in tryptophan-supplemented medium; seven were nitrogen fixer, and four were able to solubilize inorganic phosphate in vitro. Four different morphotypes were genotypically identified based on IGS-RFLP fingerprinting and representative of each morphotype was identified by 16S rRNA gene sequencing analysis except Gram-positive putative Bacillus sp. Based on 16S rRNA gene sequence analysis, bacterial isolates AJK-3 and AJK-9 showing multiple PGP-traits were identified as Stenotrophomonas spp. while AJK-7 showed equal homologies to Acetobacter pasteurianus and Stenotrophomonas specie. Plant inoculation studies indicated that these Plant growth-promoting rhizobacteria (PGPR) strains provided a significant increase in shoot and root length, and shoot and root biomass. A significant increase in shoot N contents (up to 76%) and root N contents (up to 32%) was observed over the un-inoculated control. The study indicates the potential of these PGPR for inoculums production or biofertilizers for enhancing growth and nutrient content of wheat and other crops under field conditions. The study is the first report of wheat associated bacterial diversity in the Himalayan region of Rawalakot, AJK. PMID:25852661

  10. Isolation and characterization of plant growth-promoting rhizobacteria from wheat rhizosphere and their effect on plant growth promotion

    PubMed Central

    Majeed, Afshan; Hameed, Sohail; Imran, Asma; Rahim, Nasir

    2015-01-01

    The present study was conducted to characterize the native plant growth promoting (PGP) bacteria from wheat rhizosphere and root-endosphere in the Himalayan region of Rawalakot, Azad Jammu and Kashmir (AJK), Pakistan. Nine bacterial isolates were purified, screened in vitro for PGP characteristics and evaluated for their beneficial effects on the early growth of wheat (Triticum aestivum L.). Among nine bacterial isolates, seven were able to produce indole-3- acetic acid in tryptophan-supplemented medium; seven were nitrogen fixer, and four were able to solubilize inorganic phosphate in vitro. Four different morphotypes were genotypically identified based on IGS-RFLP fingerprinting and representative of each morphotype was identified by 16S rRNA gene sequencing analysis except Gram-positive putative Bacillus sp. Based on 16S rRNA gene sequence analysis, bacterial isolates AJK-3 and AJK-9 showing multiple PGP-traits were identified as Stenotrophomonas spp. while AJK-7 showed equal homologies to Acetobacter pasteurianus and Stenotrophomonas specie. Plant inoculation studies indicated that these Plant growth-promoting rhizobacteria (PGPR) strains provided a significant increase in shoot and root length, and shoot and root biomass. A significant increase in shoot N contents (up to 76%) and root N contents (up to 32%) was observed over the un-inoculated control. The study indicates the potential of these PGPR for inoculums production or biofertilizers for enhancing growth and nutrient content of wheat and other crops under field conditions. The study is the first report of wheat associated bacterial diversity in the Himalayan region of Rawalakot, AJK. PMID:25852661

  11. Isolation of Pantoea ananatis from sugarcane and characterization of its potential for plant growth promotion.

    PubMed

    da Silva, J F; Barbosa, R R; de Souza, A N; da Motta, O V; Teixeira, G N; Carvalho, V S; de Souza, A L S R; de Souza Filho, G A

    2015-01-01

    Each year, approximately 170 million metric tons of chemical fertilizer are consumed by global agriculture. Furthermore, some chemical fertilizers contain toxic by-products and their long-term use may contaminate groundwater, lakes, and rivers. The use of plant growth-promoting bacteria may be a cost-effective strategy for partially replacing conventional chemical fertilizers, and may become an integrated plant nutrient solution for sustainable crop production. The main direct bacteria-activated mechanisms of plant growth promotion are based on improvement of nutrient acquisition, siderophore biosynthesis, nitrogen fixation, and hormonal stimulation. The aim of this study was to isolate and identify bacteria with growth-promoting activities from sugarcane. We extracted the bacterial isolate SCB4789F-1 from sugarcane leaves and characterized it with regard to its profile of growth-promoting activities, including its ability to colonize Arabidopsis thaliana. Based on its biochemical characteristics and 16S rDNA sequence analysis, this isolate was identified as Pantoea ananatis. The bacteria were efficient at phosphate and zinc solubilization, and production of siderophores and indole-3-acetic acid in vitro. The isolate was characterized by Gram staining, resistance to antibiotics, and use of carbon sources. This is the first report on zinc solubilization in vitro by this bacterium, and on plant growth promotion following its inoculation into A. thaliana. The beneficial effects to plants of this bacterium justify future analysis of inoculation of economically relevant crops. PMID:26634494

  12. Growth and characterization of CdTe on GaAs/Si substrates

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, G.; Nouhi, A.; Liu, J.

    1988-01-01

    Epitaxial CdTe has been grown on both (100) GaAs/Si and (111) GaAs/Si substrates. A combination of molecular beam epitaxy and metal organic chemical vapor deposition have been employed to achieve this growth. The GaAs layers are grown in Si substrates by molecular beam epitaxy, followed by the growth of CdTe on GaAs/Si substra by metalorganic chemical vapor deposition. X-ray diffraction, photoluminescence, and scanning electron microscopy have been used to characterize the CdTe films.

  13. MBE growth and interfaces characterizations of strained HgTe/CdTe topological insulators

    NASA Astrophysics Data System (ADS)

    Thomas, C.; Baudry, X.; Barnes, J. P.; Veillerot, M.; Jouneau, P. H.; Pouget, S.; Crauste, O.; Meunier, T.; Lévy, L. P.; Ballet, P.

    2015-09-01

    Topological insulator materials like HgTe exhibit unique electronic properties at their interfaces and so peculiar attention has to be paid concerning the growth optimization. Molecular beam epitaxy of tensile-strained HgTe/CdTe is investigated as a function of the growth temperature. Crystal quality is checked by using high resolution X-rays diffraction. By combining several material characterization techniques such as scanning transmission electronic microscopy, time-of-flight secondary ion mass spectroscopy and X-rays reflectivity, we report sharp interface morphology with nanometer-scale Hg/Cd diffusion lengths.

  14. Molecular Beam Epitaxial (MBE) Growth and Characterization of Thin Films of Semiconductor Tin

    NASA Astrophysics Data System (ADS)

    Folkes, P.; Taylor, P.; Rong, C.; Nichols, B.; Hier, H.; Burke, R.; Neupane, M.

    Recent theoretical predictions that a two-dimensional monolayer of semiconductor tin is a two-dimensional topological insulator and experimental evidence of three-dimensional topological insulator behavior in strained ultrathin films of semiconductor tin grown by MBE on InSb has generated intense research interest. This research is primarily focused on the MBE growth and topological characteristics of ultrathin films of semiconductor tin. In this talk we present results of a study on the MBE growth and the transport, structural and optical characterization of thin films of semiconductor tin on several different substrates.

  15. Temporal evolution of flow regimes in urbanizing basins

    NASA Astrophysics Data System (ADS)

    Mejia, A.; Rossel, F.; Gironas, J. A.; Jovanovic, T.

    2014-12-01

    We characterize the temporal evolution of the flow regime of urbanizing basins. By urbanizing basins, we mean basins that have experienced urban growth during their observation period. To represent the flow regime, we use flow duration curves (FDCs). We compute the FDCs using a stochastic model of daily streamflow for urban basins. In this case, the model aids in discerning the influence of key factors (e.g., climate, land use change, stormwater managenment conditions, and the slow and fast properties of the hydrologic response) on streamflow. To implement the model, we first divide the complete observation period of a given urban basin into intervals of equal duration, e.g. 5 years. Subsequently, we apply the model to each interval and this is how we capture the influence of land use changes and climatic fluctuations on the flow regime. We apply this modeling framework to 14 urbanizing basins in the Baltimore-Washington DC region. Results from this application indicate consistent changes in the temporal evolution of the altered flow regimes, which can largely be explained by the progressive redistribution with urban growth of water from slow subsurface runoff and evapotranspiration to fast urban runoff. We also use the modeling framework to determine indicators of ecohydrological alteration for urbanizing basins. The application of these indicators to our study area suggests that the flow regime is sensitive to alterations up to a certain level of urbanization after which sensitivity seems to level off. The flow regime also seems to be relatively more resistant to alterations for both the smaller and larger levels of urbanization considered. In the future, we would like to extend the application of the proposed modeling framework to other metropolitan areas.

  16. Physiological and biochemical characterization of Azospirillum brasilense strains commonly used as plant growth-promoting rhizobacteria.

    PubMed

    Di Salvo, Luciana P; Silva, Esdras; Teixeira, Kátia R S; Cote, Rosalba Esquivel; Pereyra, M Alejandra; García de Salamone, Inés E

    2014-12-01

    Azospirillum is a plant growth-promoting rhizobacteria (PGPR) genus vastly studied and utilized as agriculture inoculants. Isolation of new strains under different environmental conditions allows the access to the genetic diversity and improves the success of inoculation procedures. Historically, the isolation of this genus has been performed by the use of some traditional culture media. In this work we characterized the physiology and biochemistry of five different A. brasilense strains, commonly used as cereal inoculants. The aim of this work is to contribute to pose into revision some concepts concerning the most used protocols to isolate and characterize this bacterium. We characterized their growth in different traditional and non-traditional culture media, evaluated some PGPR mechanisms and characterized their profiles of fatty acid methyl esters and carbon-source utilization. This work shows, for the first time, differences in both profiles, and ACC deaminase activity of A. brasilense strains. Also, we show unexpected results obtained in some of the evaluated culture media. Results obtained here and an exhaustive knowledge revision revealed that it is not appropriate to conclude about bacterial species without analyzing several strains. Also, it is necessary to continue developing studies and laboratory techniques to improve the isolation and characterization protocols. PMID:25138314

  17. The characterization of small fatigue crack growth in PH13-8 molybdenum stainless steel

    NASA Astrophysics Data System (ADS)

    Jin, Ohchang

    The rotor hubs of Navy CH-46 helicopters have been made of 4340 steel and had extensive corrosion fatigue problems. Since these helicopters have to be used until the year 2020, the Navy decided to replace 4340 steel with PH 13-8 Mo stainless steel. Because the rotors are exposed to high frequency high cycle fatigue, small fatigue cracks are important in estimating remaining lifetime of the components. The objective of this study was to characterize the small crack growth behavior in the PH 13-8 Mo stainless steel under various loading conditions. Constant amplitude loading was conducted at the stress ratios, R, 0.1 and 0.4. The crack growth rate was affected by the microstructures in early stage of the growth, mainly by the size of the martensite packets and oscillated up to the crack length of 200 mum. It was found that the crack growth rate was little influenced by the stress amplitudes and stress ratios. In addition, the small crack growth rate was found to be similar to the long crack growth rate at R = 0.1 and 0.4. Overload tests and simple block loading were performed to understand load interaction effects on the small crack growth rate. The overload tests indicated that the crack growth rate was little affected by the overload. This might result from the fact that the overload ratio used in this study was low (<1.3). However, the results of the simple block loading showed overall crack growth retardation. The compressive residual stress present at the notch root of the specimen tested at R = 0.1 may lower the effective stress ratio, Reff, from 0.1 to negative R, and may result in the crack growth retardation. The small crack growth behavior was also examined under the saltwater. There was no difference in the crack growth rate between under air and under saltwater. In addition, the crack growth rate of the specimens tested under the saltwater was not affected by the test frequencies of 10, 1 and 0.1 Hz. It was shown that under the saltwater the PH 13-8 Mo

  18. Growth and characterization of large, high quality single crystal diamond substrates via microwave plasma assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Nad, Shreya

    Single crystal diamond (SCD) substrates can be utilized in a wide range of applications. Important issues in the chemical vapor deposition (CVD) of such substrates include: shrinking of the SCD substrate area, stress and cracking, high defect density and hence low electronic quality and low optical quality due to high nitrogen impurities. The primary objective of this thesis is to begin to address these issues and to find possible solutions for enhancing the substrate dimensions and simultaneously improving the quality of the grown substrates. The deposition of SCD substrates is carried out in a microwave cavity plasma reactor via the microwave plasma assisted chemical vapor deposition technique. The operation of the reactor was first optimized to determine the safe and efficient operating regime. By adjusting the matching of the reactor cavity with the help of four internal tuning length variables, the system was further matched to operate at a maximum overall microwave coupling efficiency of ˜ 98%. Even with adjustments in the substrate holder position, the reactor remains well matched with a coupling efficiency of ˜ 95% indicating good experimental performance over a wide range of operating conditions. SCD substrates were synthesized at a high pressure of 240 Torr and with a high absorbed power density of 500 W/cm3. To counter the issue of shrinking substrate size during growth, the effect of different substrate holder designs was studied. An increase in the substrate dimensions (1.23 -- 2.5 times) after growth was achieved when the sides of the seeds were shielded from the intense microwave electromagnetic fields in a pocket holder design. Using such pocket holders, high growth rates of 16 -- 32 mum/hr were obtained for growth times of 8 -- 72 hours. The polycrystalline diamond rim deposition was minimized/eliminated from these growth runs, hence successfully enlarging the substrate size. Several synthesized CVD SCD substrates were laser cut and separated

  19. Chemical vapour deposition growth and Raman characterization of graphene layers and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lai, Y.-C.; Rafailov, P. M.; Vlaikova, E.; Marinova, V.; Lin, S. H.; Yu, P.; Yu, S.-C.; Chi, G. C.; Dimitrov, D.; Sveshtarov, P.; Mehandjiev, V.; Gospodinov, M. M.

    2016-02-01

    Single-layer graphene films were grown by chemical vapour deposition (CVD) on Cu foil. The CVD process was complemented by plasma enhancement to grow also vertically aligned multiwalled carbon nanotubes using Ni nanoparticles as catalyst. The obtained samples were characterized by Raman spectroscopy analysis. Nature of defects in the samples and optimal growth conditions leading to achieve high quality of graphene and carbon nanotubes are discussed.

  20. Bubble Size Control to Improve Oxygen-Based Bleaching: Characterization of Flow Regimes in Pulp-Water-Gas Three-Phase Flows

    SciTech Connect

    S.M. Ghiaasiaan and Seppo Karrila

    2006-03-20

    Flow characteristics of fibrous paper pulp-water-air slurries were investigated in a vertical circular column 1.8 m long, with 5.08 cm diameter. Flow structures, gas holdup (void fraction), and the geometric and population characteristics of gas bubbles were experimentally investigated, using visual observation, Gamma-ray densitometry, and flash X-ray photography. Five distinct flow regimes could be visually identified: dispersed bubbly, layered bubbly, plug, churn-turbulent, and slug. Flow regime maps were constructed, and the regime transition lines were found to be sensitive to consistency. The feasibility of using artificial neural networks (ANNs) for the identification of the flow regimes, using the statistical characteristics of pressure fluctuations measured by a single pressure sensor, was demonstrated. Local pressure fluctuations at a station were recorded with a minimally-intrusive transducer. Three-layer, feed-forward ANNs were designed that could identify the four major flow patterns (bubbly, plug, churn, and slug) well. The feasibility of a transportable artificial neural network (ANN) - based technique for the classification of flow regimes was also examined. Local pressures were recorded at three different locations using three independent but similar transducers. An ANN was designed, trained and successfully tested for the classification of the flow regimes using one of the normalized pressure signals (from Sensor 1). The ANN trained and tested for Sensor 1 predicted the flow regimes reasonably well when applied directly to the other two sensors, indicating a good deal of transportability. An ANN-based method was also developed, whereby the power spectrum density characteristics of other sensors were adjusted before they were used as input to the ANN that was based on Sensor 1 alone. The method improved the predictions. The gas-liquid interfacial surface area concentration was also measured in the study. The gas absorption technique was applied

  1. Isolation and characterization of fluorescent pseudomonads and their effect on plant growth promotion.

    PubMed

    Anitha, G; Kumudini, B S

    2014-07-01

    Seven isolates of fluorescent pseudomonads were evaluated for their effect on plant growth promoting traits, both under normal and saline conditions using tomato plants. Fifteen rhizosphere samples from crop fields' of rice, chilly, ragi, beans and garden soils from different regions of India were collected and used for further study. They were characterized morphologically and biochemically which led to a conclusion that they may belong to genus Pseudomonas. They were also analyzed for their plant growth promoting activities such as production of indole acetic acid, siderophore, hydrogen cyanide and ammonia. It was observed that all the isolates were able to produce these compounds, but to varying extent. But, isolate JUPF37 produced highest followed by JUPF32. Study showed that out of seven isolates of fluorescent pseudomonads, JUPF37 showed highest plant growth promoting traits both under normal and saline conditions. PMID:25004745

  2. Computer modeling of dendritic web growth processes and characterization of the material

    NASA Technical Reports Server (NTRS)

    Seidensticker, R. G.; Kothmann, R. E.; Mchugh, J. P.; Duncan, C. S.; Hopkins, R. H.; Blais, P. D.; Davis, J. R.; Rohatgi, A.

    1978-01-01

    High area throughput rate will be required for the economical production of silicon dendritic web for solar cells. Web width depends largely on the temperature distribution on the melt surface while growth speed is controlled by the dissipation of the latent heat of fusion. Thermal models were developed to investigate each of these aspects, and were used to engineer the design of laboratory equipment capable of producing crystals over 4 cm wide; growth speeds up to 10 cm/min were achieved. The web crystals were characterized by resistivity, lifetime and etch pit density data as well as by detailed solar cell I-V data. Solar cells ranged in efficiency from about 10 to 14.5% (AM-1) depending on growth conditions. Cells with lower efficiency displayed lowered bulk lifetime believed to be due to surface contamination.

  3. Growth and characterization of uniform ZnO films as piezoelectric materials using a hydrothermal growth technique

    NASA Astrophysics Data System (ADS)

    Makarona, E.; Fritz, C.; Niarchos, G.; Speliotis, Th.; Arapoyanni, A.; Tsamis, C.

    2011-06-01

    ZnO nanostructures, especially in the form of dense arrays of nanorods or belts have the ability to efficiently convert mechanical energy to electrical energy. One of the drawbacks though for the exploitation of nanorod technology for commercial devices is the ability to make the electrical contacts to these nanostructured piezoelectric converting elements. Although technologies have been developed that provide solutions for electrical contact issues, metal contact on uniform thin films are much simpler, and can readily be implemented to commercial mass-produced applications. At the same time it is known that high piezoelectric coefficients ZnO uniform films with columnar grains having their c-axis perpendicular to the substrate are required. In this work, we investigate the growth of uniform ZnO films, using a low temperature, low cost hydrothermal process typically used for the fabrication of ZnO nanorods. Under appropriate conditions coalescence of the nanorods occur resulting in uniform films with a columnar structure. The study focuses on understanding the role of the growth factors in order to be able to fully control the proposed process. Moreover, the hydrothermal method is further exploited for the fabrication of uniform ZnO nanostructures on patterned substrates with Au interdigitated electrodes (IDE) using standard lithography as a proof-of-concept of the applicability of the method to standard microfabrication techniques. The piezoelectric films with the IDEs are electrically characterized in order to assess the electrical properties of the grown films. From this analysis, process conditions have been identified for the growth of uniform nanostructured ZnO films, suitable for piezoelectric microgenerators.

  4. Effects of antibiotic growth promoter and characterization of ecological succession in Swine gut microbiota.

    PubMed

    Unno, Tatsuya; Kim, Jung-Man; Guevarra, Robin B; Nguyen, Son G

    2015-04-01

    Ever since the ban on antibiotic growth promoters (AGPs), the livestock death rate has increased owing to pathogenic bacterial infections. There is a need of developing AGP alternatives; however, the mechanisms by which AGP enhances livestock growth performance are not clearly understood. In this study, we fed 3-week-old swine for 9 weeks with and without AGPs containing chlortetracycline, sulfathiazole, and penicillin to investigate the effects of AGPs on swine gut microbiota. Microbial community analysis was done based on bacterial 16S rRNA genes using MiSeq. The use of AGP showed no growth promoting effect, but inhibited the growth of potential pathogens during the early growth stage. Our results showed the significant increase in species richness after the stabilization of gut microbiota during the post-weaning period (4-week-old). Moreover, the swine gut microbiota was divided into four clusters based on the distribution of operational taxonomic units, which was significantly correlated to the swine weight regardless of AGP treatments. Taxonomic abundance analysis indicated a negative correlation between host weight and the abundance of the family Prevotellaceae species, but showed positive correlation to the abundance of the family Spirochaetaceae, Clostridiaceae_1, and Peptostreptococcaeae species. Although no growth performance enhancement was observed, the use of AGP inhibited the potential pathogens in the early growth stage of swine. In addition, our results indicated the ecological succession of swine gut microbiota according to swine weight. Here, we present a characterization of swine gut microbiota with respect to the effects of AGPs on growth performance. PMID:25370726

  5. Evaluation of Delamination Growth Characterization Methods Under Mode I Fatigue Loading

    NASA Technical Reports Server (NTRS)

    Murri, Gretchen B.

    2012-01-01

    Reliable delamination characterization data for laminated composites are needed for input to analytical models of structures to predict delamination. The double-cantilevered beam (DCB) specimen is used with laminated composites to measure fracture toughness, G(sub Ic), delamination onset strain energy release rate, and growth rate data under cyclic loading. In the current study, DCB specimens of IM7/8552 graphite/epoxy supplied by two different manufacturers were tested in static and fatigue to compare the measured characterization data from the two sources, and to evaluate a proposed ASTM standard for generating Paris Law equations. Static results were used to generate compliance calibration constants for the fatigue data, and a delamination resistance curve, G(sub IR), which was used to determine the effects of fiber-bridging on delamination growth. Specimens were tested in fatigue at a cyclic G(sub Imax) level equal to 50, 40 or 30% of G(sub Ic), to determine a delamination onset curve and delamination growth rate. The delamination onset curve equations had similar exponents and the same trends. Delamination growth rate was calculated by fitting a Paris Law to the da/dN versus G(sub Imax) data. Both a 2-point and a 7-point data reduction method were used and the Paris Law equations were compared. To determine the effects of fiber-bridging, growth rate results were normalized by the delamination resistance curve for each material and compared to the non-normalized results. Paris Law exponents were found to decrease by 31% to 37% due to normalizing the growth data. Normalizing the data also greatly reduced the amount of scatter between the different specimens. Visual data records from the fatigue testing were used to calculate individual compliance calibration constants from the fatigue data for some of the specimens. The resulting da/dN versus G(sub Imax) plots showed much improved repeatability between specimens. Gretchen

  6. Cloud regimes as phase transitions

    NASA Astrophysics Data System (ADS)

    Stechmann, Samuel N.; Hottovy, Scott

    2016-06-01

    Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes -- open versus closed cells -- fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. With this new conceptual viewpoint, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions.

  7. THE DYNAMIC REGIME CONCEPT FOR ECOSYSTEM MANAGEMENT AND RESTORATION

    EPA Science Inventory

    Dynamic regimes of ecosystems are multidimensional basis of attraction, characterized by particular species communities and ecosystems processes. Ecosystem patterns and processes rarely respond linerarly to disturbances, and the nonlinear cynamic regime concept offers a more real...

  8. Characterization of Mode 1 and Mode 2 delamination growth and thresholds in graphite/peek composites

    NASA Technical Reports Server (NTRS)

    Martin, Roderick H.; Murri, Gretchen B.

    1988-01-01

    Composite materials often fail by delamination. The onset and growth of delamination in AS4/PEEK, a tough thermoplastic matrix composite, was characterized for mode 1 and mode 2 loadings, using the Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) test specimens. Delamination growth per fatigue cycle, da/dN, was related to strain energy release rate, G, by means of a power law. However, the exponents of these power laws were too large for them to be adequately used as a life prediction tool. A small error in the estimated applied loads could lead to large errors in the delamination growth rates. Hence strain energy release rate thresholds, G sub th, below which no delamination would occur were also measured. Mode 1 and 2 threshold G values for no delamination growth were found by monitoring the number of cycles to delamination onset in the DCB and ENF specimens. The maximum applied G for which no delamination growth had occurred until at least 1,000,000 cycles was considered the threshold strain energy release rate. Comments are given on how testing effects, facial interference or delamination front damage, may invalidate the experimental determination of the constants in the expression.

  9. In-situ characterization of growth and interfaces in a-Si:H devices

    SciTech Connect

    Collins, R.W.; Wronski, C.R.; An, I.; Li, Y. )

    1992-12-01

    This report describes the in-situ characterization of growth and interfaces in amorphous silicon (a-Si:H) devices. The growth of a-Si:H by plasma-enhanced chemical vapor deposition (PECVD) is complex and involves many gas-phase and solid-surface chemical and physical processes, which are influenced by charged particle bombardment, ultraviolet light exposure, etc. The research consisted of two broad components. The first involved preparing a-Si:H by optimum'' PECVD and exposing the film to atomic hydrogen in-situ at the growth temperature. The processes of H-diffusion and incorporation in the exposed film were studied by spectroscopic ellipsometry, giving a picture of the processes by which the chemical potential in the film equilibrates with that in the gas phase. The properties of thin films were then prepared by alternating optimum'' PECVD growth and hydrogen exposure. Film properties were then studied again. The second component of the research is discussed only briefly in this report, as it is an outgrowth of previous work on single-wavelength ellipsometry. With the new spectroscopic capability developed at Penn State, it is now possible to quantify the nucleation and growth process of a-Si:H films.

  10. Atomically flat areas on silicon (001) and (111): Fabrication by evaporation or growth and defect characterization

    NASA Astrophysics Data System (ADS)

    Lee, Doohan

    As the dimensions of devices such as field effect transistors, optical devices and layered quantum well structures are decreased, it may be critical to have surfaces and interfaces that are extremely smooth and have no atomic steps at those locations on a wafer where devices will be fabricated and to understand the characteristics of those surfaces. For this work, we have eliminated the atomic steps on Si(111) and Si(001) vicinal surfaces by high temperature annealing and epitaxial growth in the step flow regime on patterned Si substrates with ridges and mesas respectively. In both the annealing and growth cases, the characteristics of the step clearing process as well as the stability of the step free areas are different for Si(111) and Si(001). It is more difficult to make step free regions on Si(001) than on Si(111) mainly due to the smaller adatom diffusivity on Si(001). Excessive annealing (or growth) on large step free areas leads to the formation of circular vacancy pits (or adatom islands). Anisotropic surface diffusion and stress on Si(001) due to the (1 x 2) and (2 x 1) reconstructions lead to interesting step distributions on quenched and slowly cooled Si(001) surfaces which are initially step free. Quenching experiments can give information about the nature and concentrations of point defects on the step free terraces. The result of the quenching experiments are very dependent on quenching conditions such as quenching rate, applied stress, and temperature from which the samples are quenched. The quenched Si(111) surfaces may exhibit some degree of disorder in the reconstructed regions or island formation. A series of experiments have been performed to try to relate the room temperature observations to the defect characteristics at high temperature.

  11. Propagation Regime of Iron Dust Flames

    NASA Technical Reports Server (NTRS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew J.

    2012-01-01

    A flame propagating through an iron-dust mixture can propagate in two asymptotic regimes. When the characteristic time of heat transfer between particles is much smaller than the characteristic time of particle combustion, the flame propagates in the continuum regime where the heat released by reacting particles can be modelled as a space-averaged function. In contrast, when the characteristic time of heat transfer is much larger than the particle reaction time, the flame can no longer be treated as a continuum due to dominating effects associated with the discrete nature of the particle reaction. The discrete regime is characterized by weak dependence of the flame speed on the oxygen concentration compared to the continuum regime. The discrete regime is observed in flames propagating through an iron dust cloud within a gas mixture containing xenon, while the continuum regime is obtained when xenon is substituted with helium.

  12. Material growth and characterization directed toward improving III-V heterojunction solar cells

    NASA Technical Reports Server (NTRS)

    Stefanakos, E. K.; Alexander, W. E.; Collis, W.; Abul-Fadl, A.

    1979-01-01

    In addition to the existing materials growth laboratory, the photolithographic facility and the device testing facility were completed. The majority of equipment for data acquisition, solar cell testing, materials growth and device characterization were received and are being put into operation. In the research part of the program, GaAs and GaA1As layers were grown reproducibly on GaAs substrates. These grown layers were characterized as to surface morphology, thickness and thickness uniformity. The liquid phase epitaxial growth process was used to fabricate p-n junctions in Ga(1-x)A1(x)As. Sequential deposition of two alloy layers was accomplished and detailed analysis of the effect of substrate quality and dopant on the GaA1As layer quality is presented. Finally, solar cell structures were formed by growing a thin p-GaA1As layer upon an epitaxial n-GaA1As layer. The energy gap corresponding to the long wavelength cutoff of the spectral response characteristic was 1.51-1.63 eV. Theoretical calculations of the spectral response were matched to the measured response.

  13. Integral parameters for characterizing water, energy, and aeration properties of soilless plant growth media

    NASA Astrophysics Data System (ADS)

    Chamindu Deepagoda, T. K. K.; Chen Lopez, Jose Choc; Møldrup, Per; de Jonge, Lis Wollesen; Tuller, Markus

    2013-10-01

    Over the last decade there has been a significant shift in global agricultural practice. Because the rapid increase of human population poses unprecedented challenges to production of an adequate and economically feasible food supply for undernourished populations, soilless greenhouse production systems are regaining increased worldwide attention. The optimal control of water availability and aeration is an essential prerequisite to successfully operate plant growth systems with soilless substrates such as aggregated foamed glass, perlite, rockwool, coconut coir, or mixtures thereof. While there are considerable empirical and theoretical efforts devoted to characterize water retention and aeration substrate properties, a holistic, physically-based approach considering water retention and aeration concurrently is lacking. In this study, the previously developed concept of integral water storage and energy was expanded to dual-porosity substrates and an analog integral oxygen diffusivity parameter was introduced to simultaneously characterize aeration properties of four common soilless greenhouse growth media. Integral parameters were derived for greenhouse crops in general, as well as for tomatoes. The integral approach provided important insights for irrigation management and for potential optimization of substrate properties. Furthermore, an observed relationship between the integral parameters for water availability and oxygen diffusivity can be potentially applied for the design of advanced irrigation and management strategies to ensure stress-free growth conditions, while conserving water resources.

  14. Crystal Growth, Characterization and Fabrication of Cadmium Zinc Telluride-based Nuclear Detectors

    NASA Astrophysics Data System (ADS)

    Krishna, Ramesh M.

    crystal homogeneity of other modern CZT growth techniques. However, information about crystals grown with this method has not been undertaken in a comprehensive way thus far. In this work, Cd0.9Zn0.1Te is grown using the solvent-growth method using zone-refined precursor materials loaded into carbon-coated quartz ampoules. Ampoules were sealed and crystal growth was performed using crystal growth furnaces built in-house at USC. Ingots 1-2" in diameter produced using the solvent-growth method were wafered, processed, and polished for characterization. Semiconductor characterization is performed on the CZT crystals to determine band gap, elemental stoichiometry, and electrical resistivity. Surface modification studies were undertaken to determine if surface leakage current can be reduced using sulfur passivation. XPS studies were used to confirm the effects of passivation on the surface states, and electrical characterization was performed to measure the effects of passivation on the CZT crystals. Deep-level and surface defect studies were conducted on the CZT samples to determine the type and intensity of defects present in the crystals which may affect detector performance. Finally, nuclear detectors were fabricated and characterized using analog and digital radiation detection systems to measure their performance and energy resolution.

  15. STING Promotes the Growth of Tumors Characterized by Low Antigenicity via IDO Activation.

    PubMed

    Lemos, Henrique; Mohamed, Eslam; Huang, Lei; Ou, Rong; Pacholczyk, Gabriela; Arbab, Ali S; Munn, David; Mellor, Andrew L

    2016-04-15

    Cytosolic DNA sensing is an important process during the innate immune response that activates the stimulator of interferon genes (STING) adaptor and induces IFN-I. STING incites spontaneous immunity during immunogenic tumor growth and accordingly, STING agonists induce regression of therapy-resistant tumors. However DNA, STING agonists, and apoptotic cells can also promote tolerogenic responses via STING by activating immunoregulatory mechanisms such as indoleamine 2,3 dioxygenase (IDO). Here, we show that IDO activity induced by STING activity in the tumor microenvironment (TME) promoted the growth of Lewis lung carcinoma (LLC). Although STING also induced IDO in tumor-draining lymph nodes (TDLN) during EL4 thymoma growth, this event was insufficient to promote tumorigenesis. In the LLC model, STING ablation enhanced CD8(+) T-cell infiltration and tumor cell killing while decreasing myeloid-derived suppressor cell infiltration and IL10 production in the TME. Depletion of CD8(+) T cells also eliminated the growth disadvantage of LLC tumors in STING-deficient mice, indicating that STING signaling attenuated CD8(+) T-cell effector functions during tumorigenesis. In contrast with native LLC tumors, STING signaling neither promoted growth of neoantigen-expressing LLC, nor did it induce IDO in TDLN. Similarly, STING failed to promote growth of B16 melanoma or to induce IDO activity in TDLN in this setting. Thus, our results show how STING-dependent DNA sensing can enhance tolerogenic states in tumors characterized by low antigenicity and how IDO inhibition can overcome this state by attenuating tumor tolerance. Furthermore, our results reveal a greater complexity in the role of STING signaling in cancer, underscoring how innate immune pathways in the TME modify tumorigenesis in distinct tumor settings, with implications for designing effective immunotherapy trials. Cancer Res; 76(8); 2076-81. ©2016 AACR. PMID:26964621

  16. Effect of different feeding regimes on pre-weaning growth rumen fermentation and its influence on post-weaning performance of lambs.

    PubMed

    Bhatt, R S; Tripathi, M K; Verma, D L; Karim, S A

    2009-10-01

    Influence of pre-weaning live weight on post-weaning growth performance was assessed on thirty-nine 15-day-old Indian native lambs, randomly fed in three equal groups until 180 days of age. During pre-weaning phase lambs were maintained under feeding regimen of grazing (C-0; Control), grazing and ad lib creep mixture supplementation (C-AL) or grazing, with ad lib creep mixture and milk replacer supplementation (C-ALMR). Lambs were allowed to suckle respective dam in morning and evening till 90 days of age, and fed ad lib green leaves of Ailanthus excelsa after grazing. After weaning all lambs were maintained on grazing and ad lib finisher concentrates supplementation. Pre-weaning performance of lambs in terms of weaning weight (17.2 kg), average daily gain (ADG; 154 g) and feed conversion ratio 3.73 was higher (p < 0.01) in C-ALMR lambs but total gain and ADG were similar among three groups during post-weaning phase. However, improved pre-weaning plane of nutrition and growth rate increased (p < 0.01) finishing weight (FW) of lambs in C-AL, 33 kg and C-ALMR, 32 kg. Dry matter intake was significantly (p < 0.01) higher in C-AL and C-ALMR lambs due to combined effect of feeding. Rumen pH was lowest (p = 0.049) in C-AL lambs. Rumen ciliate protozoa population (10(4)/ml) decreased in C-ALMR lambs (4.3) but increased in C-AL lambs (50.0) more so in C-0 Lambs (19.8). Concentrate feeding of C-AL lamb improved nutrient digestibility. Lambs of C-0 group consumed more DM during post-weaning phase that improved growth performance, while nutrient digestibility was not affected by pre-weaning nutrition. Thus, pre-weaning nutrition has significant influence on FW, however influence of milk replacer feeding on lamb growth need further studies. PMID:19141102

  17. Characterizing the growth to detonation in PETN and HNS with small-scale PDV cutback experiments

    NASA Astrophysics Data System (ADS)

    Wixom, Ryan; Yarrington, Cole; Knepper, Robert; Tappan, Alexander; Olles, Joseph; Zelenok, Matthew; A-Team

    2015-06-01

    For many decades, cutback experiments have been used to characterize the equation of state and growth to steady detonation in explosive formulations. More recently, embedded gauges have been used to capture the growth to steady detonation in gas-gun impacted samples. Data resulting from these experiments are extremely valuable for parameterizing equation of state and reaction models used in hydrocode simulations. Due to the extremely fast growth to detonation in typical detonator explosives, cutback and embedded gauge experiments are extremely difficult, if not impossible. Using frequency shifted photonic Doppler velocimetry (PDV) we have measured particle velocity histories from explosive films impacted with electrically driven flyers. By varying the sample thickness and impact conditions we were able to capture the growth from inert shock to full detonation pressure within distances as short as 100 μm. These data were used to assess and improve burn-model parameterization and equations of state for simulating shock initiation. Additionally, we discuss details of the experiment and data analysis regarding the most accurate possible determination of the velocity spike.

  18. Evaluation of Delamination Onset and Growth Characterization Methods under Mode I Fatigue Loading

    NASA Technical Reports Server (NTRS)

    Murri, Gretchen B.

    2013-01-01

    Double-cantilevered beam specimens of IM7/8552 graphite/epoxy from two different manufacturers were tested in static and fatigue to compare the material characterization data and to evaluate a proposed ASTM standard for generating Paris Law equations for delamination growth. Static results were used to generate compliance calibration constants for reducing the fatigue data, and a delamination resistance curve, GIR, for each material. Specimens were tested in fatigue at different initial cyclic GImax levels to determine a delamination onset curve and the delamination growth rate. The delamination onset curve equations were similar for the two sources. Delamination growth rate was calculated by plotting da/dN versus GImax on a log-log scale and fitting a Paris Law. Two different data reduction methods were used to calculate da/dN. To determine the effects of fiber-bridging, growth results were normalized by the delamination resistance curves. Paris Law exponents decreased by 31% to 37% after normalizing the data. Visual data records from the fatigue tests were used to calculate individual compliance constants from the fatigue data. The resulting da/dN versus GImax plots showed improved repeatability for each source, compared to using averaged static data. The Paris Law expressions for the two sources showed the closest agreement using the individually fit compliance data.

  19. ZnO:HCl single crystals: Thermodynamic analysis of CVT system, feature of growth and characterization

    NASA Astrophysics Data System (ADS)

    Colibaba, G. V.

    2016-06-01

    The full thermodynamic analysis of using HCl as a chemical vapor transport (CVT) agent (TA) for ZnO single crystals growth in closed growth chambers, including 16 chemical species, is carried out for wide temperature and loaded TA pressure ranges. The influence of the growth temperature, of the TA density and of the undercooling on the rate of ZnO mass transport was investigated theoretically and experimentally. It is shown that the mass transport is diffusion-limited at about 1050 °C, and it is limited by kinetics of the CVT reaction at lower temperatures. It is experimentally shown that using HCl favors obtaining void-free n-ZnO crystals with controllable electrical parameters, it reduces the effect of adhesiveness to the walls of the growth chamber. The characterization by the photoluminescence spectra, the transmission spectra and the electrical properties in the wide temperature range allowed analyzing energy spectra of Cl-containing stable defects in ZnO and electrical activity of Cl donors. Some methods of activation energy correction for Cl-containing centers are discussed.

  20. Dynamic Characterization of Dendrite Deposition and Growth in Li-Surface by Electrochemical Impedance Spectroscopy

    SciTech Connect

    Hernandez-Maya, R; Rosas, O; Saunders, J; Castaneda, H

    2015-01-13

    The evolution of dendrite formation is characterized by DC and AC electrochemical techniques. Interfacial mechanisms for lithium deposition are described and quantified by electrochemical impedance spectroscopy (EIS) between a lithium electrode and a graphite electrode. The initiation and growth of dendrites in the lithium surface due to the cathodic polarization conditions following anodic dissolution emulate long term cycling process occurring in the lithium electrodes. The dendrite initiation at the lithium/organic electrolyte interface is proposed to be performed through a combination of layering and interfacial reactions during different cathodic conditions. The growth is proposed to be performed by surface geometrical deposition. In this work, we use EIS in galvanostatic mode to assess the initiation and growth stages of dendrites by the accumulation of precipitates formed under different current conditions. The lithium/organic solvent experimental system using frequency domain techniques is validated by the theoretical approach using a deterministic model that accounts for the faradaic processes at the interface assuming a coverage fraction of the electrodic surface affected by the dendritic growth. (C) 2015 The Electrochemical Society. All rights reserved.

  1. Synthesis and Characterization of High-Purity Tellurium Nanowires via Self-seed-Assisted Growth Approach

    NASA Astrophysics Data System (ADS)

    Li, Ying; Zhao, Wen-yu; Mu, Xin; Liu, Xing; He, Dan-qi; Zhu, Wan-ting; Zhang, Qing-jie

    2016-03-01

    Nanowires have attracted intense attention in recent years due to their novel physical properties. In this work, we prepare high-purity tellurium nanowires through the self-seed-assisted growth method previously developed by us. The tellurium seeds were firstly synthesized by reducing Na2TeO3 in the ice water with NaBH4. The high-purity tellurium nanowires with a diameter of 40-50 nm and a length of several tens of micrometers were then grown on tellurium seeds by reducing Na2TeO3 with hydrazine hydrate. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were employed to characterize the crystal structure, microstructure, and growth direction of tellurium seeds and nanowires. The effects of temperature, time, surfactant and tellurium seeds on microstructures of tellurium nanowires has also been investigated. The synthesis conditions of tellurium seeds and nanowires was optimized. The selected area electron diffraction pattern confirms that the growth direction of tellurium nanowires is parallel to [0001] direction. It was discovered that high-purity tellurium nanowires with high aspect ratio can be synthesized by precisely controlling the temperature to adjust the nucleation rate of the tellurium nuclei, selecting the appropriate surfactant to induce the coordination along the macromolecular chain, and using tellurium seeds as the templates of the epitaxial growth of tellurium nuclei.

  2. Synthesis and Characterization of High-Purity Bismuth Nanowires via Seed-Assisted Growth Approach

    NASA Astrophysics Data System (ADS)

    Mu, Xin; Zhao, Wen-Yu; He, Dan-Qi; Zhou, Hong-Yu; Zhu, Wan-Ting; Zhang, Qing-Jie

    2015-06-01

    Nanowires are considered as high-performance thermoelectric materials with large Seebeck coefficients due to quantum confinement and low thermal conductivity because of enhanced boundary scattering of phonons. In this work, a seed-assisted growth method has been developed to synthesize high-purity bismuth nanowires. The bismuth seeds were first synthesized by reducing BiCl3 in the ice water with NaBH4. The high-purity bismuth nanowires about 40-50 nm in diameter and several tens of micrometers in length were then grown on bismuth seeds by reducing NaBiO3 with ethylene glycol. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were employed to characterize the crystal structure, microstructure, and growth direction of the bismuth seeds and nanowires. The effects of temperature, reductant, and bismuth seeds template on the microstructures of the bismuth nanowires were also investigated. The synthesis conditions of bismuth seeds and nanowires were optimized. The selected area electron diffraction pattern confirms that the growth direction of bismuth nanowires is parallel to [] direction. It was discovered that high-purity bismuth nanowires with high aspect ratio can be synthesized by precisely controlling the temperature to adjust the nucleation rate of the bismuth nuclei, selecting the appropriate reductant to maintain a low nucleation rate, and using bismuth seeds as the template of the epitaxial growth of the bismuth nuclei.

  3. The Incompatibility of Living Systems: Characterizing Growth-Induced Incompatibilities in Expanded Skin.

    PubMed

    Buganza Tepole, Adrian; Gart, Michael; Purnell, Chad A; Gosain, Arun K; Kuhl, Ellen

    2016-05-01

    Skin expansion is a common surgical technique to correct large cutaneous defects. Selecting a successful expansion protocol is solely based on the experience and personal preference of the operating surgeon. Skin expansion could be improved by predictive computational simulations. Towards this goal, we model skin expansion using the continuum framework of finite growth. This approach crucially relies on the concept of incompatible configurations. However, aside from the classical opening angle experiment, our current understanding of growth-induced incompatibilities remains rather vague. Here we visualize and characterize incompatibilities in living systems using skin expansion in a porcine model: We implanted and inflated two expanders, crescent, and spherical, and filled them to 225 cc throughout a period of 21 days. To quantify the residual strains developed during this period, we excised the expanded skin patches and subdivided them into smaller pieces. Skin growth averaged 1.17 times the original area for the spherical and 1.10 for the crescent expander, and displayed significant regional variations. When subdivided into smaller pieces, the grown skin patches retracted heterogeneously and confirmed the existence of incompatibilities. Understanding skin growth through mechanical stretch will allow surgeons to improve-and ultimately personalize-preoperative treatment planning in plastic and reconstructive surgery. PMID:26416721

  4. ZnO:HCl single crystals: Thermodynamic analysis of CVT system, feature of growth and characterization

    NASA Astrophysics Data System (ADS)

    Colibaba, G. V.

    2016-06-01

    The full thermodynamic analysis of using HCl as a chemical vapor transport (CVT) agent (TA) for ZnO single crystals growth in closed growth chambers, including 16 chemical species, is carried out for wide temperature and loaded TA pressure ranges. The influence of the growth temperature, of the TA density and of the undercooling on the rate of ZnO mass transport was investigated theoretically and experimentally. It is shown that the mass transport is diffusion-limited at about 1050 °C, and it is limited by kinetics of the CVT reaction at lower temperatures. It is experimentally shown that using HCl favors obtaining void-free n-ZnO crystals with controllable electrical parameters, it reduces the effect of adhesiveness to the walls of the growth chamber. The characterization by the photoluminescence spectra, the transmission spectra and the electrical properties in the wide temperature range allowed analyzing energy spectra of Cl-containing stable defects in ZnO and electrical activity of Cl donors. Some methods of activation energy correction for Cl-containing centers are discussed.

  5. Supplying materials needed for grain growth characterizations of nano-grained UO2

    SciTech Connect

    Mo, Kun; Miao, Yinbin; Yun, Di; Jamison, Laura M.; Lian, Jie; Yao, Tiankei

    2015-09-30

    This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructure based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize our preliminary synchrotron radiation experiments at APS to determine the grain size of nanograin UO2. The methodology and experimental setup developed in this experiment can directly apply to the proposed in-situ grain growth measurements. The investigation of the grain growth kinetics was conducted based on isothermal annealing and grain growth characterization as functions of duration and temperature. The kinetic parameters such as activation energy for grain growth for UO2 with different stoichiometry are obtained and compared with molecular dynamics (MD) simulations.

  6. Synchrotron characterization of nanograined UO2 grain growth

    SciTech Connect

    Mo, Kun; Miao, Yinbin; Yun, Di; Jamison, Laura M.; Lian, Jie; Yao, Tiankei

    2015-09-30

    This activity is supported by the US Nuclear Energy Advanced Modeling and Simulation (NEAMS) Fuels Product Line (FPL) and aims at providing experimental data for the validation of the mesoscale simulation code MARMOT. MARMOT is a mesoscale multiphysics code that predicts the coevolution of microstructure and properties within reactor fuel during its lifetime in the reactor. It is an important component of the Moose-Bison-Marmot (MBM) code suite that has been developed by Idaho National Laboratory (INL) to enable next generation fuel performance modeling capability as part of the NEAMS Program FPL. In order to ensure the accuracy of the microstructure based materials models being developed within the MARMOT code, extensive validation efforts must be carried out. In this report, we summarize our preliminary synchrotron radiation experiments at APS to determine the grain size of nanograin UO2. The methodology and experimental setup developed in this experiment can directly apply to the proposed in-situ grain growth measurements. The investigation of the grain growth kinetics was conducted based on isothermal annealing and grain growth characterization as functions of duration and temperature. The kinetic parameters such as activation energy for grain growth for UO2 with different stoichiometry are obtained and compared with molecular dynamics (MD) simulations.

  7. A Novel Method for Characterizing Fatigue Delamination Growth Under Mode I Using the Double Cantilever Beam Specimen

    NASA Technical Reports Server (NTRS)

    Carvalho, Nelson; Murri, G.

    2014-01-01

    A novel method is proposed to obtain Mode I delamination growth rate from a Double Cantilever Beam (DCB) specimen. In the proposed method, Unidirectional (UD) DCB specimens are tested in fatigue at different initial maximum energy release rates levels. The growth rate data obtained in the first increments of crack growth at each maximum energy release rate level are used to generate a Paris Law equation, which characterizes delamination growth rate without fiber-bridging, and can also be used to determine a delamination onset curve. The remaining delamination growth rate data from each test are used to determine a modified Paris law, which characterizes the delamination growth rate in a DCB specimen, explicitly accounting for fiber-bridging. The proposed expression captures well the scatter in experimental data obtained using the DCB specimens, suggesting its adequacy. The Paris Law characterizing delamination growth rate without fiber-bridging predicts higher delamination growth rates for the same maximum energy release rate applied, leading to a conservative estimate for delamination growth. This is particularly relevant, since in generic ply interfaces, fiber-bridging is less predominant than in UD DCB specimens. Failing to account for fiber-bridging in UD DCB specimens may underestimate the delamination growth rate, yielding non-conservative predictions.

  8. Biotechnological Production of Docosahexaenoic Acid Using Aurantiochytrium limacinum: Carbon Sources Comparison And Growth Characterization.

    PubMed

    Abad, Sergi; Turon, Xavier

    2015-12-01

    Aurantiochytrium limacinum, a marine heterotrophic protist/microalga has shown interesting yields of docosahexaenoic acid (DHA) when cultured with different carbon sources: glucose, pure and crude glycerol. A complete study in a lab-scale fermenter allowed for the characterization and comparison of the growth kinetic parameters corresponding to each carbon source. Artificial Marine Medium (AMM) with glucose, pure and crude glycerol offered similar biomass yields. The net growth rates (0.10-0.12 h(-1)), biomass (0.7-0.8 g cells/g Substrate) and product (0.14-0.15 g DHA/g cells) yields, as well as DHA productivity were similar using the three carbon sources. Viable potential applications to valorize crude glycerol are envisioned to avoid an environmental problem due to the excess of byproduct. PMID:26690180

  9. Characterizing the snorkeling respiration and growth of Shewanella decolorationis S12.

    PubMed

    Yang, Yonggang; Guo, Jun; Sun, Guoping; Xu, Meiying

    2013-01-01

    Microbial electrochemical snorkel (MES) reactor is a simplified bioreactor based on microbial fuel cells (MFCs) and has been suggested to be a promising approach to solve many environmental problems. However, the microbial processes in MES reactors have not yet been characterized. This study shows that Shewanella decolorationis S12 can use the conductive snorkel as direct electron acceptor for respiration and growth. Similar with current-generating biofilms, cellular viability in MES biofilms decreased with the distance from snorkel. MES reactors showed more rapid cell growth and substrate consumption than MFCs. Although the biomass density of MES biofilm was higher than that of anode biofilms, the current-generating capacity and electrochemical activity of MES biofilm were lower, which could be attributed to the lower cytochrome c expression in MES biofilm caused by the higher redox potential of MES. These microbiological and electrochemical properties are essential for the further development of MES reactors. PMID:23201531

  10. Flux growth and characterization of cuprorivaite: the influence of temperature, flux, and silica source

    NASA Astrophysics Data System (ADS)

    Bloise, A.; Abd El Salam, S.; De Luca, R.; Crisci, G. M.; Miriello, D.

    2016-07-01

    Single crystals of cuprorivaite (CaCuSi4O10), one of the oldest synthetic color pigments of Egyptian history, have been synthesized by slow-cooling flux method. Several runs were carried out at temperatures between 800 and 960 °C and with reaction times ranging from 10 to 72 h. The starting materials and run products were characterized by binocular microscope, X-ray powder diffraction, scanning electron microscopy with annexed energy-dispersive spectrometry, and μ-Raman spectroscopy. The effects of growth parameters (temperature, flux, silica source) on yield and size of crystals were studied. The growth of cuprorivaite depends greatly on the starting materials: they are observed as run products only using natron as flux. Furthermore, colorimetric analysis performed on the synthesizing pigment was compared with the archeological samples present in the literature in order to value similarities and differences.